OK, let's take a look at chords today. I am not going to explain you what those letters C, D etc. mean, because - well, if you made it to YourChords.com website, I'm pretty sure that you already know. Am I a Sherlock or what? :)
When it comes to chords, I think I can really help you with giving you a free (you are getting used to that, aren't you, haha?) list of pretty much all the chord variations you can think of. You can find it here - chord variations diagram.
Or if you feel like printing it, I have prepared a PDF version for you as well - chord variations diagram PDF.
Another thing we should mention are the barre chords because they usually cause quite a lot of problems to beginners. Fretting a barre chord is actually the same as retuning the guitar a number of half-steps higher, playing the original open chord - it's actually very similar to the use of a capodaster. You use your index finger to cover all of the strings at a certain fret and then you hold a specific chord with the rest of your fingers. For example, your index finger is across the fifth fret and your three other fingers are holding the E major chord - this way you are actually playing an A major chord, which is five half-steps higher than E!
So, how can you get those barre chords to ring clearly? You have to slightly bend your index finger and apply pressure on the strings with it. Then just strum slowly to make sure each string is sounding. Once you get there, you just need a couple of days' practice and you will be all set.