If you've got money to burn, I'd say go for it (online course). I took it myself and my score went up 200 points. Personally, it was worth the wad of cash I laid out for it. The online course is basically the same as the class course except that you do it at your own pace and you can watch the classroom lectures on your computer if you wish (if you're one of those auditory learners).
It basically teaches you how to look at and take the GRE along with relevant review aids such as vocab words, loads of practice sets for the quantitative portion, writing skill strategies for the analytic writing section, etc. It helps to get you ready for test day using "Kaplan's tried and true test-taking strategies".
If you've been out of school for a while, I think it is a great, but expensive, tool.
I guess you could find the workbooks on Ebay, etc. if money is an issue.