Ok I've heard about it but I'm not up to par on the jazz scene. I just thought it sounded interesting and was wondering if you could post the names of some good acid jazz bands or songs.

Acid jazz is sort of a jazz wine cooler, if Miles, Monk and Mingus are the VSOP XXX cognac. A gentle introduction to the world of jazz, it's fun, in a jammy way, but it's barely jazz. A funky feeling with an electronic boost. For the young at heart.

A disc that I would recommend is St. Germaine's "Tourist" , on blue Note. Small samples of jazz, blues, etc. worked into an infectious deep groove.

Isn't acid jazz another name for trip-hop?

It's not really a style I pay attention to, but as far as my understanding of it goes, it's a dancable, funk-inspired post-fusion style of light Jazz that incorporates electronic dance elements...

...but I could be completely off-base, considering that it's really not my cup of tea at all.

Off the top of my head, about the only group I can think of to suggest is Groove Collective.

Is stuff like Portishead and Massive Attack acid jazz?

No, I can't say I've found any connection between Acid Jazz and Trip-Hop other than their use of electronics here and there.

As there's hardly a trace of anything resembling Jazz in the music of Portishead and Massive Attack, I really don't think it'd be a good label.

I've heard Portishead and Massive Attack labelled as acid jazz before, and I can kind of see why, but I agree with Seba in that there really isn't much jazz to speak of in their music. Acid jazz is electronic first, but there are jazz elements, mostly manifested in samples from what I've heard. It's almost a misnomer, really. I listen to acid jazz now and again, and I quite enjoy it.

I'd go with St Germaine or even Xploding PLastix (Amateur Girlfriends album, at least), for examples.