Local and Online sources for electronic and some mechanical parts
Local "surplus" vendors - Electronics and mechanical:
These vendors fall into the surplus store category. You can often find components and mechanical parts for pennies on the dollar. They may or may not have exactly what you're looking for, but they are almost always worth a try. And while browsing you may see a solution that had not previously occurred to you!
Kearny Mesa area. Good source for electronic components of all types. And advice. Manny's the man!
Kearny Mesa area. These guys have mainly mechanical components, but quite a variety of electro-mechanical components also. Plus heat shrink tubing and cables.
El Cajon. Mostly electronics but also motors, mechanical parts, wire/cable, and more...
El Cajon. Just down the street from California Electronics above. Lots of test and measurement systems. Surplus military stuff. Also electronic components, pneumatics, and a large etc.
Local retail vendors - Electronics and mechanical:
Willy's has both an online store and walk in service. All new stuff, not surplus.
Sort of hesitate to recommend, but Fry's does sometimes have what you need. Electronic components, tools, wire, connectors, test instruments. Try SD Electronic Supply first.
These guys specialize in both normal and odd cables. You might try them if you have an unusual cable requirement, or need some discussion on solving an odd cabling problem.
Miramar area off of Miramar Road. Near Marine Air Station Miramar. Industrial hardware. Tons of fasteners (screws, bolts, nuts, steel, stainless, nylon), pneumatic fittings, tools, glues, wire, hose, tubing, chemicals, and much more. If you need something local and you think Home Depot or Ace Hardware might have it, don't even bother. Just go directly to Marshall's.
Kearny Mesa area. The MAE machine shop has some selection in metals and materials, but you may need something they don't have. Industrial Metal Supply has a pretty good selection of aluminum, steel, brass, and copper available in sheets, bars, rods, and specialized forms. You can buy in small amounts, like rod by the foot, or sheet by the square foot.
And speaking of industrial hardware, McMaster-Carr is in LA, but they are almost local. They do such a large business volume that they have their own huge fleet of trucks to deliver their stuff. Fast! If you order today you'll get it tomorrow. Great website, and great phone help in identifying a part. In general, McMaster-Carr has it.
Large Industrial Electronic Parts Houses:
These vendors have huge inventory. They all have their own online search engines to help you find the part you need. You can order either over the phone or online. Shipping can be as fast as you want to pay for it, from overnight to 4-5 days. For a given part if you shop these vendors you may find some pricing differences, but on most parts everyone knows what everyone else is selling them for. Different parts houses carry different manufacturers products, so you may not find everything at one vendor.
The OEMs, i.e. the companies who actually design and manufacture electronic components, often do not sell directly to end users. They use distribution channels through high volume distributors, or the electronics parts houses mentioned above. But often they will give stuff away! You may find that a particular part which seems perfect for your project is on back order at the parts houses, or has a long lead time. What to do? It's always worth a phone call to the OEM and ask for samples. Explain that you are an engineering student at UCSD and you are working on a project where their part would be a perfect fit. You can also request samples online. Most OEMs have links for sample requests. Tip: These online links usually ask, in regard to your design "What is the annual volume". Just type in 5000. You need to do some research first so that you know exactly which part number you want. The p/n will determine the 'package' type; through-hole or surface mount (SMT). Through-hole is easier to work with for prototyping, but almost all new ICs are now available in SMT only. Here are some good companies:
Smaller hobby-oriented electronics vendors:
These vendors don't have the breadth of parts that the large parts houses do, but they can be worth a try.
The following is a sample of these sorts of vendors, in no particular order. There are many more.
Gadgets, surplus, power supplies, motors, overruns... :
These vendors offer a large variety of parts and components. Their stock is often acquired from overruns at a manufacturer, or surplus components from obsoleted equipment. You'll find power supplies, motors, electronic components, solenoids, some optics and mechanical parts, tools, valves, and generally quite a grab bag of "stuff". If they have it, they have it; if they don't they don't. If you design something purchased here into a project and a year later you want to build another one, you may find the original part you bought is no longer available. But these guys are always worth a try, and it's good just to have an idea of what they have. Generally cheap prices also! Marlin P. Jones is especially good for a large selection of power supplies. Check All Electronics for motors.
Embedded systems, sensors, robotics and more:
The name sounds like maybe the result of some sort of wiring error, but they are a great company with a huge offering. They are oriented toward embedded microcontroller projects, and offer many many sensors. What's good is that they sell not just the sensor, but often have a breakout board with the sensor mounted on it, meaning you can start using it right away. This is important if the sensor only comes in a micro-sized multi-pin surface mount package, very difficult to solder yourself. Lots of good tutorials also. Recommended.
Another odd company name, but a great company also. They have a broad offering in motor controllers and motor drivers (there's a difference). Lots of robotics and sensors also.
Like it sounds, these guys are robotics types for the most part. They have an interesting mix of sensors also. Worth checking out their site.
This is a well-established company with absolutely fantastic customer support. They offer a wide variety of sensors and robotics. Parallax sort of started the personal microcontroller field with their Basic Stamp, which they still sell and support. They more recently have developed their own high-powered multi-tasking (8 simultaneous tasks) chip called the Propellor. You program it in their own compiler language called Spin (of course). They have great documentation with all their products, example programs to use with their sensors, and all-around great support generally.
Some specialty items:
You can buy LEDs most anywhere. These guys, like the name says, sell super bright ones.
Here's a large selection of LCD displays at modest prices. Good selection. They also sell graphical LCDs, LED displays, and much more.
Encoders can be expensive. This company sells a couple of inexpensive rotary encoders, both incremental and absolute types. Check out the E4P rotary incremental encoder, or the MAE3 absolute rotary encoder.
GeckoDrive: Great company for stepper motor drivers and stepper motors. Their G251X stepper driver is often a good solution, economically priced. Servo drivers also. Reasonable prices. Their FAQ includes an extensive 'How-To' and is a whole motor education in itself. Great after-sales phone tech support; you can often talk directly to the engineer who designed it. Highly recommended.
There are hundreds of add-on boards for the Arduino system. It can be a bit difficult trying to identify a board which provides the best fit to the function you need. ShieldList.org is a good place to start. Below are a few recommended boards:
And of course, don't forget...
Your project might require a high-value sensor or actuator for which you have insufficient budget. Look for it on ebay. Chances are often pretty good you can find what you need at a hefty discount over what the same or similar might cost to buy new. For example, mass flow controllers: new cost typically $1500-2000; ebay cost typically $25-100.
Amazon started out sell books online. That was then. They have now spread their tentacles far and wide, and you can buy almost anything on Amazon, either directly or from 3rd party vendors.The Amazon pricing of often pretty good also!