If you don't know what Twitter is, I suggest you find out.
One of the tools I use when trying to keep up with trends in MtG prices is Twitter. After seeing the TurboFog deck on the MtG.com site, I had no idea what people thought of it. Then I fired up Twitter, where I follow a bunch of Magic players. Twitterers were in a tweeting frenzy over the new deck, and I knew it would be a factor at Regionals.
Twitter is fantastic because it allows players to see realtime metagame shifts, so if you're not on Twitter already, get on! You can follow my updates by clicking the link in the sidebar. You should also be following TWITTER.COM / STARCITYBUYER, which is updated when SCG changes their buy list. I even have Twitter set to text message me on my cell phone when they post an update. Realtime market updates are a very powerful tool to have if you're serious about trading for profit, so if there are any other sites out there that do anything like this, post a comment below!