http://unison-db.org/
Unison is a comprehensive set of protein sequences with lots of precomputed results of many types. Unison was designed primarily for rapid mining of complex combinations of protein features. There's a simple homology-based structure viewer that can map SNPs and arbitrary regions onto structures.
The Unison source and website were released under the Academic Free License, and the data are released under the Creative Commons. There's a public PostgreSQL service (Try 'psql -h unison-db.org -U PUBLIC -d unison'). Command line tools are available. Loading and computing are automated and incremental, and coordinated by a makefile.
See http://unison-db.org/tour/ and http://unison-db.org/doc/ for examples and connection information.
The site is currently hosted at Genentech, my former employer. Unison is used internally at Genentech, but not updated as often as I used to (but there's a page with versions of source databases).
-Reece