Birch is a simple proxy or tunnel application with a filter mechanism for line based application protocols built on TCP. Initially it was written to add encryption in a transparent way to the IRC protocol but as the encryption mechanism is implemented in a modular way, it is not restricted to just supporting encryption. Filters can be supplied via Java's Service Provider mechanism. A CLI and a GUI are available.
sec-wall is a feature-packed security proxy that supports SSL/TLS, WS-Security, HTTP Auth Basic/Digest, extensible authentication schemes based on custom HTTP headers and XPath expressions, powerful URL matching/rewriting, and an optional header enrichment. It's a security wall with which you can conveniently fence otherwise defenseless backend servers.