tongmeiz:
Hello, I am new to Arduino and I have been searching around online for assorted things such as breadboards, sensors, and LEDS. The shipping from the official site is way to expensive. Do you have any recommendations for a site that sells many different components for reasonable prices (and shipping)? I live in the U.S.
Would you be willing to try surplus components? For breadboards, LEDs, transistors, switches, motors, etc - these surplus vendors have worked well for me:
If you feel adventurous, and don't mind spending a few days sorting the parts, one or two of these boxes from Electronic Goldmine:
http://www.goldmine-elec-products.com/prodinfo.asp?number=G9321
...can be well worth the money.
For other things like "sensors" and servos, the cheapest would probably be Ebay; you might also look at:
http://www.seeedstudio.com/depot/
http://store.nkcelectronics.com/
http://stores.ebay.com/Tayda2009
Not saying the above vendors are inexpensive or "cheapest" in all things, but you should be able to find something among them all. Keep looking, I probably have 100 or more other links I haven't shared for various suppliers of all kinds of things (not just electronics). Practice your google-fu, research the forums out there, troll ebay; you won't believe what is out there.
Also: Have you done any local searching? Have you looked in the yellow pages under "electronics parts" or "electronics surplus"? You might have a wonderful supplier in your own backyard. If you live in or near any reasonably large city, you likely do have something - it may look like a junk yard, but its there. Case in point: I live in the Phoenix, Arizona area. Electronic Goldmine is across town (unfortunately, they only offer a web front - no walk-ins). There is also a place I love to shop at called "Apache Reclamation and Electronics" (where old electronics and other junk goes to die); they also have a place in New Mexico (lots of surplus places in that state, what with all the government labs and such). There's also a place called Equipment Exchange. Then there's ASU Surplus (you can sometimes find interesting things there). There's a few other places down in Tuscon as well.
I also like to shop at thrift stores (Goodwill is a favorite haunt) for interesting items I can take apart and/or re-use. Sometimes you run across things you wouldn't normally expect: Last week, for instance, I found an R/C airplane, with servos, motors, ESC, etc (no transmitter, though) - got it for a few dollars. Toy R/C cars make great platforms for robotic vehicles and such; sometimes you can find old construction kits (like Lego, Erector, etc) that can be used for numerous purposes.
I often find old Polaroid cameras with ultrasonic distance sensors in them at Goodwill (look for Sun 660 and Spectra models); there's several resources describing how to remove and reuse the sensors from the cameras (an article from last year in Servo Magazine, IIRC, detailed how to hook them up to an Arduino). You shouldn't spend more than $5.00 on such a camera, and the sensor you get is virtually equivalent to the SensComp 6500 (http://www.senscomp.com/). On top of that you'll find a motor or two, some lenses, and maybe a few other parts.
As you can probably tell, I'm a "surplus and junk" connoisseur; I'll only buy new parts if I have no other way to get a particular device (or, if I were doing small-scale manufacturing or something where I needed a dependable supply).