Earlier this year Niclas released a DXA module for Alpaca Forms. The module is packed with features including: a form designer, pluggable handlers to take care of posted form data, protection against CSRF attacks, both .NET and JAVA support.
Damian writes about extending the SDL Knowlege Center (Tridion Docs) GUI, and mentions SDL Web (Tridion Sites) just enough to add the article to this review ;)