Hi all, I want to buy some electronics components ( resistor , capacitor and transistor) but there are lots and lots of variety to choose from for example there are many resistors and capacitors with different value and many different types of transistors.
Please tell me which are the most commonly used values of resistor and capacitor( both electrolytic and ceramic ) and which transistor types are good.
As a hobbyist of UNO, the following components could have in collection:
1/4 watt rated resistors: 1k, 2.2k, 4.7k, 10k (10 each)
Transistors: C828, C1384, BC327 (pnp) (5 each)
Capacitors: 104 (0.1uF/63V AC), 10uF/16V (DC), 1uF/10V (DC) (5 each)
Common uses for resistor:
LED current limiting for small LEDs. 220 ohms to 1k is right range for this.
pull-up and pull-down resistors. 10k is fine normally.
Not usually much else needed for digital electronics.
For analog electronics you need a full range of values in a kit, 10 ohms to 1M, to be useful for
experimentation.
For decoupling 0.1µF ceramic are needed for every chip, plus 10 to 100µF electrolytic for the
board.
Without knowing what you want to do its hard to say much more about capacitors, there are
a wide variety of types in use for analog and RF signal processing.
Transistors: 2N2222 or similar switching transistor is good for upto about 0.5A, otherwise
logic-level MOSFETs will be needed for higher currents/loads.
For basic hobby electronics stuff, ebay is your friend.
Search ebay for "resistor kit" and "capacitor kit" - get a set of resistors, ceramic capacitors (make sure it goes all the way to 10uF. 10uF ceramic caps are very useful, and that it either includes 18~22pF, or buy one of those yourself), and electrolytic capacitors (you care most about 47~1000uF range here, and you won't need many). Consider also buying an additional 100-pack of 0.1uF ceramics, you need at least one for every digital IC, for decoupling.
Transistors? Guess what - try "transistor kit" on ebay! Assortments of the popular hobbyist-transistors. As an aside, those popular hobbyist transistors are all really old parts; they're popular because there are so many circuits and hobbyist-targeted writeups that use them.
Some diodes and schottky diodes. I was going to write some recommended ones - but the good sellers on ebay have already made cheap diode kits too.
Snag a few small 10k linear potentiometers, and some tactile pushbuttons (the 2-pin 6x6x5mm ones on ebay are, as you can easily use them with breadboard; the more common 4-pin ones in that size don't fit as well into breadboard).
If you like colored LEDs, get a string of WS2812's (aka Neopixel).
I would be inclined to say that everyone experimenting with electronics should have a few 555 timer IC's and some 339 comparators. And some ULN2003/2803's.
If you're interested in robotics, get some of the hobby servos.
These kits and parts on ebay are CHEAP - be aware that the ones that ship from china take weeks to arrive. You can also get dirt-cheap arduino clones, sensors, and modules there. If there are things you are interested in, try searching ebay for the thing you want to sense and the word arduino. Most of these are made-in-china clones of products from Adafruit or Sparkfun - only typically at a fraction of the price (you track down the adafruit/sparkfun tutorials to figure out how to use them - the ebay sellers don't provide documentation)
When buying specific values or a specific component, the big electronics supply houses are similarly priced to ebay, but with full specs, fast shipping and much better selection (so much better that it can be overwhelming). Digikey, mouser - farnell in the UK. They don't have cheap modules or boards like ebay does - in fact everything they sell that isn't just a component is exorbitantly priced.
DrAzzy:
I would be inclined to say that everyone experimenting with electronics should have a few 555 timer IC's and some 339 comparators. And some ULN2003/2803's.
It has been pointed out in a recent thread, that you do not want the old NE555 but rather the CMOS version whose performance is much closer to the theoretical function that the logic diagrams would have you believe. 
ULN2003/2803's (and Darlington transistors in general) have extremely poor performance particularly at 5 V and are basically obsolete - used only because there are really old tutorials featuring them. If you understand the specifics of what you might use therm for, there will generally be a much more appropriate device, most often (and almost always when used in association with a microcontroller) the TPIC6B595 or similar.
DrAzzy:
When buying specific values or a specific component, the big electronics supply houses are similarly priced to eBay, but with full specs, fast shipping and much better selection (so much better that it can be overwhelming).
But only "similarly priced" when purchased in large quantities and for someone living in the US due to the immense mail costs whereas China Mail is heavily state-subsidised.
I don't grok where the two week delay is in China Mail; whether it is in the loading/ unloading shipping containers at the source end or deliberate delays by recipient countries whose mail systems are delivering it in phenomenal quantities for free.