As far as actual Free Comic Book Day stuff:
Marvel has both a Guardians of the Galaxy book and a Rocket Raccoon book out for FCBD. The GotG book should definitely be worth grabbing.
Dark Horse usually has something good for FCBD, and it usually goes pretty quickly. This year it's Avatar (not the movie)/Hellboy/Juice Squeezers. Juice Squeezers is a really neat kid-friendly Dave Lapham (Stray Bullets) book.
There's a 2000 A.D. FCBD anthology that I am definitely going to try to grab if I can.
For the kids, the Top Shelf Kids Club and Kaboom! anthologies are always good. The only comics I've ever gotten for my daughter have been FCBD things, but she really loves some of them. I probably like Top Shelf Kids Club more than she does just because of the quality of the illustration. (I'll be picking up the Hello Kitty thing for her this year, probably.)
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As for general comics:
I'm several months behind in reading, but the best Marvel books for the past couple of years have been Daredevil and Hawkeye. I like the current main Avengers books a lot, but Hickman's stuff (Avengers and New Avengers) is a pretty huge, epic story that might be more of an undertaking than you want to get into. Rick Remender's Uncanny Avengers (sort of a hybrid X-Men/Avengers team) is really good and way more manageable. Thor has been really good, especially the issues with Esad Ribic on art. I haven't actually started reading it yet, but everyone seems to love Warren Ellis's new Moon Knight series. The art definitely looks great, and I have little reason to doubt that it will be a good book. Same goes for the new She-Hulk, Secret Avengers, and Winter Soldier books. Bendis's All-New Ultimate Spider-Man (Miles Morales) has been consistently good, and I think it either just re-launched or is about to. There's a new Silver Surfer book drawn by Mike Allred that looks campy and fun. Really, there are a lot of good Marvel books right now.
As for independents, Image has a ton of great books going. For the past few years Saga, Manhattan Projects, Fatale, and Prophet have been some of my favorite comics. Newer stuff like Zero, Lazarus, Sex Criminals, Satellite Sam, Velvet, Jupiter's Legacy, and Velvet has been great, too. Dave Lapham recently brought back Stray Bullets on Image after more than a 10 year hiatus, and by all accounts the new series - Stray Bullets: Killers - is great.
Everyone seems to love Afterlife with Archie, the Archie zombie book. There are some good current Vertigo books like The Wake and Sandman Overture. I don't know if you read 100 Bullets, but Azzarello and Risso recently did a sequel mini-series called Brother Lono that was good.
Also, you probably won't be able to find it in any stores, but check out Michel Fiffe's Copra. You can read the first issue free on his website here:
http://michelfiffe.com/comics/copra/index.htmlAnd right now is a good time to hate DC.