Next week you will be able to pick up Hitman: Blood Money, but until then, jump onto the Xbox Live Marketplace, and grab the demo.
For its filesize, I found the demo rather short. It will take up around 783MB of your hard drive space, and consists of one tutorial level where it walks you through every step of getting to a bad guy and killing him. The graphics are reasonable and the leve you walk through is an abandoned theme park.