Abstract Horizon is set of open source projects.
is a little desktop program that allows comparison and
synchronisation of two folders and their sub-trees of files.
is a simple HTTP server that can operate without having to conform to the J2EE standard.
Extend is a simple, highly configurable and light-weight
application container based on Spring Framework.
Mercury is set of e-mail related projects.
It currently has implementations of SMTP inbound server and IMAP 4rev1 server. Both are working
based on Maildir JavaMail implementation.
Here you can find some interesting stuff.