Dagon, I will take the bait. Most of mine is tied up long term in TSP & outside Roth in mutual funds. I set it once or twice a year and let it go.
This is how I do things, not necessarily how you should.
I do have some speculative money set aside to trade in the short term. Recently I like to find companies that have buyouts on the table that are still trading at a nice discount. Invest and just wait on the deal to close. The subprime has hurt the lending so be careful here.
I also have several stocks that I watch that trade with a higher beta since I am trying to outdo the market. These trade in a range (ie. drop to 8 then shoot up to 10 then back to 8). I trade around earnings announcement because the volume picks up for the ones I follow. I set mine up for loss limits, and also pick a price to get out and then I get out. I try to keep the emotions out of it and I do not try to get greedy, unlike Gordon Gecko. Sometimes I am in cash for 3 months or more just to be safe. Be patient and read the SEC filings closely.