If you are interested in checking out SQL Azure for free, they just extended the trial period till 3/31/2011. What it boils down to is that you get to have a 1GB web database free of charge for 3 months, Good deal if you want to evaluate what this Azure fuss is all about. If you exceed your allowance, you will get charged, but they do it in daily increments. I created a second database and kept it around for a day, I received a hefty bill of $0.10. Considering it ran as a credit card transaction, Microsoft probably lost money on that.
Also, keep in mind that you do not get charged for the master database. It shows there, you can look at it, but you can't even create tables in it.