pretty massive Sega sale going down on Xbox Live right now. Many games and DLC packs are $5 or less. In the $5 camp are Virtua Fighter 5: Final Showdown, Sonic Adventure 2, Jet Set Radio, Nights into Dreams and Crazy Taxi. Other downloads, such as Guardian Heroes, the Sega Genesis Sonic games (including Sonic CD) and Space Channel 5 Part 2 are only two bucks each. You'll also find a number of $10 Games on Demand titles, including Sonic Generations, Condemned, Sega Superstars Tennis ... and Sonic Unleashed.
Finally, if you haven't tried out Ron Gilbert's latest adventure, you can pick up The Cave for $7.50.