Hello, I'm about to buy some resistors, I would like to know which values do you recommend that are good to have to make tests etc...
I know I need values between 50 - 500 ohms for example for LEDs, I also need 4.7k (or 10k?) ohms for pull ups for my DHT22/DS18B20 sensors..
But appart from those values, which ones are good to have ready? I probably don't need values like 1 ohm, or 10 M ohm, right? Please suggest common values for arduino projects.
Thanks 
Nice Question,
I grabbed a bulk mixed pack rom my local electronics store the other day. This is a question heaps of people wopuld find useful. Same for Caps possibly?
Whenever I buy resistors I buy 1, 10, 47, 100, 220, 470, 1k, 5.6k, 10k, 56k, 100k, and 1m. I've found a use for all of them.
I use three values predominantly: 1k, 10k, and 100k.
There do seem to be just a few values that address the vast majority of my needs!
330?, 1K, 2.2K, 4.7K, 10K. 1/4W or smaller, 5% or better.
Capacitors: 100nF ceramic, 10µF electrolytic, then some larger electrolytics for filtering, value is usually not super critical, whatever you can find cheap, e.g. 100µF, 220µF, 330µF, 470µF, etc. All should be 16V or better. As for the 100nF caps, get them by the hundred, they're best with 0.1" lead spacing, I like the multilayer ceramic type (MLCC), X5R or X7R spec is best.
Thank you all 
Capacitors are slightly different.
I use a lot of 4.7u/.1uf, as well as 12pf/15pf/22pf (for crystals).
Anything else would be highly application specific and hard to say.
Mostly what I use is 220, 470,1k,10k,
My advice is buy a resistor kit - much better value than buying resistors individually. Something like http://www.rapidonline.com/Electronic-Components/MR25-Metal-film-resistor-kit-65199 or http://www.ebay.co.uk/itm/1-4W-Metal-Film-Resistor-Assort-kit-1000-pc-50-values-/220719309028?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item3363e560e4.
On the subject of leds and resistors, I recently sat and soldered resistors onto a handful of leds to save messing around when I need to use them.
Why don't they leave the factory like that... maybe in a few flavours for different voltages.
JimboZA:
On the subject of leds and resistors, I recently sat and soldered resistors onto a handful of leds to save messing around when I need to use them.Why don't they leave the factory like that... maybe in a few flavours for different voltages.
Because the resistor value you need depends not only on the voltage of the supply but also on the current you want to drive them at. You may want to drive the same LED at different currents, for example if it is multiplexed with other LEDs.
However, you can get LEDs with built-in series resistors, for example http://www.maplin.co.uk/12v-3mm-leds-35738.
JimboZA:
On the subject of leds and resistors, I recently sat and soldered resistors onto a handful of leds to save messing around when I need to use them.Why don't they leave the factory like that... maybe in a few flavours for different voltages.
Because manufacturing and selling raw resistors and leds is a very high volume very low margin commodity market. Making and selling LEDs with either a internal or soldered external resistor would turn it into a low volume speciality component and would have to have a much higher margin to make and sell profitably. I know that Radio Shack use to sell a two lead +5vdc only led that had a internal resistor installed inside the led package, also had one that blinked automatically. Not sure if they still carry either of those now.
Lefty
Unless I'm buying some weird value etc., I almost always buy resistors in lots of 100. Even from the top-shelf distributors, they're usually only a penny or two each in that quantity, and I probably end up with a lifetime supply or nearly so
From Amazon: 860 resistors for 17.99: 10 X 86 values from the E12 List (Most Common resistors)
There was another kit for 29.99 that was 4300 resistors, I bought one...
Still can't find a place for all of them, I could split them into 4 assortments all the same and one would be all I'd probably use.. Ever.
Bob
I finally bought a big pack on ebay too, it was much cheaper than buying separately on some electronic site... I paid less than 6€ (7.5$) for 1000 resistors (50 values, 20 of each) shipping included, I know I don't even need 5% of those now... but maybe in some years 8)
ebay 230688889689
One problem with resistor packs is whether you can read the values back. I bought a pack of resistors from a vendor, and somebody wrote the value on the tape in hand writing that is unreadable (and with a pen that wasn't quite permanent ink). I'm slightly color blind, and honestly, I cannot tell the difference between orange and brown on some resistors. As I use them, I've been using my label maker to relabel the resistor packs (and using sandwich bags when the resistors become loose). I was recently ordering some stuff from Adafruit, and I might buy their resistor book the next time I need to restock, as it seems to be better labeled: SMT/SMD 0805 Resistor and Capacitor Book - 3725 pieces : ID 441 : $39.95 : Adafruit Industries, Unique & fun DIY electronics and kits.
As far as I know, nobody had written the Android program that uses the camera on the phone/table to identify the resistor (and capacitor presumably) value. I seem to recall there is an iphone utility that does this, but so far on the Android side, I've only seen programs that give you a chart with the color wheels.
Though if you really want to be safe, you would use your multimeter to measure each one, though I suspect most people trust the color bands on the resistors.
I'm a little color blind so that doesn't help 
Hopefully in the kit I bought they are all sorted in individual bags (I hope..): http://www.sure-electronics.net/Modders/DC-RS013-2-b.jpg
I've never seen a resistor assortment in individual bags, Usually they come in a single bag. The resistors are "Cut Tape" with the value marked in the tape. The same goes for SMT components, Cut Tape W/hand markings, many are not very legible either. There are assortments that are better marked but they are also better priced (Typically about 4X the components actual retail value) per "Book" of parts. In part I suppose because of the novelty and mainly to reflect the cost of populating a "Parts Book" like the ones commonly sold. While I don't suffer from any color vision inadequacies, there are many times where the value is all but unreadable due to the color of the paint used to coat the body of the resistor. The two colors (band and body will make browns, oranges and reds... Difficult to decipher. An Ohm meter is a good idea when dealing with resistors Especially the 1% or 4 band resistors. SMT capacitors are a special challenge, I wound up with a small (1 X 1 cm) gold plated fixture for my capacitance meter... Later for my production people I built a 555 driving a speaker and a rotary switch for the appropriate ranging resistor so they could sort droppd loose components... which seemed to happen frequently.
Bob
