Starting today until May 5th, the online Microsoft Store is offering a free Xbox LIVE 1600 points card with you purchase certain titles. Most of the qualifying titles are in the $60 range, but there are some oddly inexpensive titles that you can take advantage of:
Dead Rising (X360) for $12.99
Soul Calibur IV (X360) for $19.95
Fable (Xbox) for $9.95
Mass Effect 2 (X360) for $19.95
Rock Band 2 (X360) for $19.95
The Beatles: Rock Band (X360) for $19.95
LEGO Batman for $19.95
And hey, if perchance you don't care for a game, you can always sell or trade it in (for more points, I suppose).