This is a question I can answer with a little bit of authority, being in a several ska bands myself.
It really depends on what you're interested in. Other than Streetlight Manifesto, there really haven't been many bands to achieve any sort of widespread success. Here are a few small bands that I've been listening to recently.. I know I'll think of more later.
The Long Johns
<spoiler=Female fronted Power-Pop Ska>The Flaming Tsunamis
<spoiler=Freaking awesome Boston Skacore>Chilled Monkey Brains
<spoiler=Another live video of marginal quality, trust me, they have recordings>
I've played shows with all of them, and I may or may not be a former member of one of them. So I can personally vouch that all of these are 100% solid bands.