Components

[RedRoomRec]

Hi, I'm new to this and was wondering about the components list. Some of the links don't give you anything which I've seen others have that same problem and the solution was to just find the same component on a different site. My question is, and this may have been covered, why when you click on the Farnell Link for capacitors, it gives you exact pieces with different values like lead spacing, ohms, capacitance, temperature max. and min. but when you click on say the LED Rapid link you get 3 different options or the 33 resistor you get like 15. So how, if I'm using digikey or mouser, do I know what values to pick for each component? Are the values in the parts list all that really matters? Also is the Atmega32/324P the component you should use? I feel like I read somewhere about using 64. I have no idea what that component is or does so any links or info on that would be much appreciated.
Thanks

[ignotus]

It's the value that matters. With resistors, get the same value and 1/8 or 1/4 watt, carbon or metal film. With capacitors, get electrolitics for the ones that have polarity marked for them in the schematics, 16v rated, and ceramic or polyester film capacitors will do for the rest.

As for the Atmega, I'd get the 644 instead of the ones you mention. This is the "brain" of the module and the 32/324 became outdated quite some time ago. Be aware that if you buy this component yourself, you'll also have to program it with the firmware yourself, using a firmware from 2010. If you want to be able to use an up-to-date firmware you'll have to order a chip from Dmitri.