I've been playing Petty Investments with my savings. Mostly I'm treating this like a video game, just playing around.
What I've learned: It's fun to buy small amounts of stocks to keep the risk low, but hard to make any percentage of $ back on that, because while gains and losses are relative to the amount of money you've invested, broker fees are flat. Therefore, a saner strategy would be to invest in chunks no smaller than, say, $300, if I plan to sell once I've made an amount of money.
Sharebuilder's site is extremely buggy and hostile, unless I'm doing real-time buys and sells.
Thusfar, I've made about $75 on an average of $1000 over about six months. This is roughly a 14% gain over a year, I'm guessing, which is pretty darn good, though because the numbers are really pretty small, it doesn't seem like much.
Right this second, everything seems to have taken a plunge, though. This is irritating, but it happens.