Roughly speaking, there are 4 endings (although there are minor changes to each of those 4 based on one of the choices you get at the end), based on a combination of two factors - the 'big' choice near the end, and your paragon/renegade alignment:
1) Save the council
2) Let the council die (Concentrate on Sovereign also goes here)
A) More Paragon than Renegade
B) More Renegade than Paragon
Combinations as follows:
1A is the standard 'paragon/good' ending - humanity is granted a seat on the council, with them going on about how awesome you and humanity are and the sacrifices you've made, etc etc, everyone is happy and nice (except all the dead human crewmembers sacrificed to save the council, of course...).
1B is slightly unusual, and not one that you'd generally see unless you specifically tried to get it to see what happens. Basically the same as 1A, but with different tone to the dialog with the council - something about you "showing that humanity is willing to do whatever it takes to succeed, and that being exactly what's necessary in these dark times" (paraphrased).
2A reforms the council in it's previous, multi-racial form, but with a human member (possibly implied to be the leader/chairman in some sense, it's a bit ambiguous).
2B is the basic 'renegade/evil' ending - you form a new, all-human council, and even if you say you don't want that (that you only let the council die because it was a pragmatic choice, and that Sovereign needed to be the priority), Udina will overrule you, saying that he's watched your actions and that you believe in forcefulness and stomping all over the little people, and blah blah humanity has to take advantage of the opportunity etc etc (very paraphrased).
Plus minor variations based on whether you recommend Anderson or Udina for a position on whatever council ends up running the show, or decide not to choose (i think in that case each option has a 'default' choice it picks - Anderson for paragon options, Udina for renegade i think; far from certain on those though, as i've always nominated Anderson, since Udina is a massive tosser who needs to go eat a bag of dicks).
At least, i think that's all right. Any corrections gladly accepted.