Eric, did you pick one? I plan to get a real estate license relatively soon, probably after earning my urban planning credential (AICP). One of my colleagues at work did the online real estate pre-license course through GIRE and liked it. He recommended also getting the book AND also doing their optional cram session.
Personally, I tried the Coldwell Banker online course and found it to be incredibly tedious clicking through the endless series of slides and questions, and not being able to progress at your own pace (being forced to answer the same questions multiple times, etc.). Then my work schedule got nuts, I didn't have time to study, and the course expired. It probably didn't help that I got sick of the online interface, either.
So the "flexible" online option is actually only so flexible. Be prepared that it is a commitment, and you will need to study pretty diligently to finish before the course expires. This is coming from someone with a masters degree, so trust me, I'm not just lazy. Personally, the social pressure of going to classes would force me to make it a priority, and I think I'd enjoy the classroom setting more anyway.
I think weekend-only courses are hard to find, because it would take so long. Did you find one that looks good?