Mass Effect had a fairly memorable supporting cast! The fascist soldier lady, the angry turtle man, the slightly too-handsome junior officer. Hope you didn't get too attached to them, however, as they won't be returning to your party in the sequel.
While some of them will feature in Mass Effect 2, none will be returning to your band of merry men/women/turtle men. Bioware's Casey Hudson:
All the squad members that you pick up are completely new characters. Some of them from races that have never been in your squad before.
It's going to be larger squad, a lot more varied and very, very different kinds of characters. Everyone that you can take with you is a different character from before.
Wonder how they're going to work in a return of the old squad members, since at last count you could kill at least two of them on every playthrough?
UPDATE - Bioware have since clarified the above statement (well...at least attempted to hose down cries of OMG NO WREX?!?!), posting on the game's official boards:
In some cases, it is possible that squad members from ME1 could end up in your ME2 squad. Again, we're trying to approach this with respect for the characters. Nobody is being clumsily shoehorned in or casually written out. All surviving squad members are at least present as NPCs with important story roles.