Please take a look at the CRing Project. Its aim is to be “an open-source textbook on commutative algebra, one simultaneously accessible to beginning undergraduates but advanced enough to cover the foundations needed for a serious study of algebraic geometry”. It just started so this might be perfect if you wanted to jump in and join. Email Akhil Mathew for more information.
Another open source algebra text is Abstract Algebra: Theory and Applications which is run by Tom Judson, Rob Beezer, and Lon Mitchell.
Let me know if learn of others (with relevance to the stacks project).