Go to top of this thread and it gives you very specific instructions. Do it, it's really cool. I really dug Velocity since the beginning, but thought I'd try something new and waddaya know, it actually works quite nicely!!!!
My ally isn't activated anymore, I just use it for testing and experimental purposes. I moved on to a Fascinate and it's pretty friggin' rad on that as well!!!!
Flash this zip in recovery 1st
Then flash Gapps zip immediately after
password if asked for it
And BAM---You have CM7 runnin' on your Ally!!!!!!