Omeka is a free, flexible, and open source web-publishing platform for the display of library, museum, archives, and scholarly collections and exhibitions. Its five-minute setup makes launching an online archive or exhibition as easy as launching a blog.
AJS is a ultra lightweight JavaScript library that is around 1 and half year old. It is hugely inspired by MochiKit, but differs by being small. The current version is only 33 KB (uncompressed), whereas MochiKit is over 100 KB