Canoo WebTest is functional web testing tool based on ANT. Siegfried wrote a M1 plugin some years ago and currently works on the M2 version.
Java Mail Server is a small stand-alone SMTP/POP3 server written by Eric Daugherty well suited for a development and testing mail server running on all platforms. Unfortunately it is under GPL and not Apache license which makes integration into existing applications impossible. Siegfried is quoted as long-standing contributor which is a very polite written statement for altogether two patches - thanks Eric ... :-)
Pnuts is a scripting language system based on JVM (think of a better Groovy) and very handy to do some dirty scripting. Siegfried is using it heavily for writing database migration scripts depending on existing Java classes.
Siegfried is the co-founder and president of the Java User Group Austria