Steve Riley does play more cajun than Zydeco, but that's a line that can be hard to distinguish. I'm not from cajun country, but Riley's music has the drive that I associate with Zydeco. And he definitely does play some zydeco.
I see zydeco as a sub-genre of cajun in much the same way as R&B or early rock is a sub-genre of blues. What Clifton Chenier did to develop Zydeco from Cajun is much the same thing that Muddy Waters did to delta blues when he moved to the city and went electric. Make it faster and louder so the dance floor goes nuts. Maybe add a drum kit or a sax and mix up the traditional sounds with some other genres. Most music ends up bluring into an mixture of the styles that influenced the various players.
If we're moving on to cajun then I can't help but recommend the best known cajun band, BeauSoleil.
One comment on Audiohorn's list, the last 2 artists, Terrence and Buckwheat, are great musicians and started playing zydeco, but IMHO have moved so far from the roots that I would not recommend them as a way to learn the genre. You may like them, but I like to learn where the music first cam from before exploring the fringes of a style.
By the way, I highly recommend seeing Beau Jacques too.
Lots of energy and a respect for the original sound. Also, I'm not sure if Clifton's son C.J Chenier is still playing, but his band gets the zydeco groove going too.
