Secret Invasion - This years huge cross-over event. Skrulls are invading, I'm sure you've heard. The second issue is getting ready to come out. It shouldn't be too hard to locate issue #1. Plus if you liked Runaways they're having a tie-in called "Runaways/Young Avengers: Secret Invasion"... duh
Kick Ass - Think Super-Bad meets Marvel. Your typical nerd wants to be a superhero, but he's got no powers. Keep in mind this is not set in the Marvel Universe, so no Wolverine team-ups in this one. The first issue may be hard to get (it sold out fast) Issue #2 just came out and I think a reprint of Issue #1 will hit shelves soon.
X-Force - Probably my favorite X-Title out right now. Wolverine leads this new covert-ops X-Men team. The art is amazing. Issue #3 is the most recent
Incredible Herc - Trust me, this comic is amazing, action packed and funny. I've never been a Herc fan but I am now. It's Herc running around with boy genius Amadeus Cho being chased by S.H.E.I.L.D. with a great conforntation between him and his brother Aeres. He took over Hulk's old comic around issue #111. I urge you to pick up some back issues or wait for the first TPB. It also helps to know the World War Hulk story and Cho.
Hulk - He got a new series, it's currently on Issue #3. This one hasn't grabed me yet however I think it'll take off in the future.
Skaar: Son of Hulk - Set to come out this summer. If you liked WWH or Planet Hulk then this is a must.
Ultimate Spider-Man - The new Venom arc is starting up soon, it might be a good time to get onboard with the best Spider-Man title out. The great thing about Ultimate Spider-Man is being able to jump into at any arc.
Thor - He's back and he's reviving Asgard. Already at issue #8. Possibly pick up the TPB when it comes out.
Fantasctic Four - Just started a new arc a few issues back with power team of Millar & Hitch (Ultimates) They promise to jump start the FF and I'm on board. If you're intrested it's gonna be a 16-issue run. Go back a few issues to #554 and you should have no problem at all getting into it.