Some fun things I did over the years:

• A multiuser/multitasking DOS-compatible OS... which ran on PC-XTs!
  
• A distributed inventory/orders system for a computer store chain. Online updates of MDB database content AND structure. In 1997.
  
• Access control system for an ISP. Kinda Rube Goldberg-ish. Lots of scripts that manipulate iptables to turn users to the login page, dhcpd to give thep IPs, cbq to assign them bandwidth etc.
  
• A security system for MS-DOS, implementing somewhat-Unix-style accounts and permissions.
  
• Clustering Asterisk PBXs for call centers and other Asterisk hacking.
  
• Autodialers with detection of human / answering machine / busy / bad number for (I'm going to Hell for this) active telemarketing. Please forgive me.
  
• A driver to integrate Skype into Asterisk. Even more Rube Goldberg-ish than the ISP login thing.
  
• Energy consumption billing through a proprietary board that "ticked" a bit in a parallel interface whenever X watts-hours had gone through path Y.
  
• Linux system-restore CDs.
  
• Satellite image acquiring through yet another proprietary expansion board, for Brazil's National Space Research Institute.
  
• REST services with Django.
  
• Remote system audits in C# using the OVAL language.
  
• For the retrocomputing fans out there: https://sourceforge.net/projects/cachars
  
• Lots more I sure forget about now.
  
  

Oh, and I also learned CUDA and Greenplum. They're neat. But I didn't get to use either in any project so far. :-/

Things I like for fun:

• Formula One and Indy racing.
  
• Reading in general, mostly nonfiction.
  
• Retrocomputing and retrogaming.
  
• Traveling, preferably overseas.
  
• Sci-fi in general, and Star Trek in particular.