It's so funny that this question has been posed. I thought for a second that I had actually posted this! :)

I'm pretty much in your same situation. I dropped out of college back in the late 90s, and the last math class that I successfully passed was Calculus II. I took a Calculus III class, but stopped going around the time I dropped out. This puts me at almost 15 years since I've attended a structure math class at the university level. Before that, I look Precalculus in high school...in 1991. I haven't had an Algebra class since 1990.

I can recall many things, but definitely NOT enough to pass a college exam. I decided that I would go back to school and start with Calculus I. After all, SURELY if I've had this material before I could easily get an A! Ahem. I could remember the basics, I could remember the rules of derivation and integration, but I couldn't remember the Trigonometry. Finding the derivative of something involving sine, cosine or tangent confounded me. At the behest of the professor, I enrolled in Precalculus. After the first week, we had a test covering the basics of Algebra. I flunked that. I couldn't remember every last detail, and it's been nearly 20 years since I've seen this material directly in a classroom environment.

After consulting with a friend, I decided to take matters into my own hands. I'm not willing to spend the time (and money) in a classroom retaking math classes, so I headed to my local Half Price Books. I'm fortunate enough to live in Dallas where we have several large stores with a massive stock of older college texts. I picked up a book on Algebra, Trigonometry and Precalculus. I also acquired the teachers manuals and student's solutions manuals for these texts, giving me a nice base of information to jog my brain. Math hasn't changed a whole lot in the last few years, and the main thing that I find that dates the books is the calculator requirement. Some of these books use a TI-85 or TI-86 in their chapter sample exercises, but these are the calculators I have lying around since my college days.

iTunesU is also an awesome source. Go search on Algebra and other math subjects to get full courses on any subject you lack. You can get older courses and cheap textbooks on Amazon if you want to precisely follow along. Th Algebra videos from Harrisburg Area Community College have helped me immensely.

As mentioned above, MIT's OCW can help you, but if you were so inclined to teach yourself mathematics with MIT's material you probably wouldn't be posting on Slashdot asking for some assistance. I don't mean this as an insult in the slightest; I'm not one to learn this type of material on my own, either!

In summary: hit iTunesU and get some FULL courses to fill you in. Go get some used, older textbooks either online or at a local used bookstore if you have such a resource in your area. Outside of these self-help options, you can always enroll at a local community college to basically start over. I know the Dallas area colleges sometimes have rolling enrollment and/or compressed schedule courses. You may find that you can plow through classes like College Algebra, Trigonometry and Precalculus in a shorter time since you're basically refreshing your knowledge.

Good luck!