TortoiseGit + Dropbox, my personnal SCM combo under Windows
Why Git ?
Because I followed the early history in 2005 and I liked the design 
Why now ?
Because I am under Windows and I feel that the windows port is ready for my personnal use with TortoiseGit.
Where is my repository ?
Just on my local drive, but if you want to opensource your project I suggest you to go on GitHub.
How to backup and get my source from an another computer ?
Dropbox ! because I already use Dropbox to sync my files online and across my computers automatically and it works very well.
If you use my referral link for Dropbox, you will have +250 Mo with your 2 Go free account. (and me too)
Finally, if the project is not a Vaporware, you can always move your repository on GitHub or somewhere else.
Go and try TortoiseGit with Dropbox