I, too, have an unorthodox background, and I also wonder if I can land a normal software job. This week, I got pulled into a slow IM conversation one night, so I read through the most recent hiring thread[1] to pass the time. There are 102 comments in that thread. I emailed five people who sounded like they had interesting offerings, and in each email included something like "I know I have an usual background, but . . ." along with a link to my github account. I had one phone interview already and I've got another one later this week and one next week.
That doesn't solve the problem of passing the interview, but if you include a candid note in your email, anyone who decides to interview you will be doing it knowing about your 'problems'; it helps to filter out companies that wouldn't be interested anyway.
If you want to pass a more traditional interviewing process, think of it as passing the final to some class. Here, I'm assuming that you've managed to pass at least one academic class in your life. This algorithms book[2] is free, and exactly what you want (it doesn't cover everything in the world; just in the important stuff, and it has good exercises that are approximately difficult as what you'll see in interviews). Pretend that's the textbook for a class you need to pass, and work through exercises until you can solve ones you haven't seen before fluently[3]. Just like cramming for an exam, you'll probably forget 90% of the material a week later, but you won't need that stuff for the vast majority of jobs anyway.
Good luck!
[1] http://news.ycombinator.com/item?id=4727241
[2] http://www.cs.berkeley.edu/~vazirani/algorithms.html
[3] If you get stuck, feel free to shoot me an email (see my profile). In theory, I ought to be able to answer your question cold. If I can't, that's a sign I need to do some review and I'd be happy to re-read the relevant material so I can explain it.