I'm with Cor, I'd definitely like to do something with Sebastian's halfblood-ness -- he's had pretty much everyone in Slytherin believe something different, so it could be interesting to see how everyone would react to him basically lying about his heritage. And he needs friends!
And I really really want to do something with Quinn too. As of now she's basically just moping about Jesse and being paranoid about St Lopez but she's definitely in the market for a new friend/love interest/anything.
Most of the stuff I do is computer-based, so even if I don't reply right away, I'm usually on from the time I wake up to the time I go to sleep. My timezone is GMT+5.5 though, which is really annoying and inconvenient, but I don't sleep much, so you should still be able to catch me online at some point during the day. :)