• Recoll is a personal text search system (desktop search) for Unix and Linux
• lesbonscomptes will help with your accounting after you've been on a holiday trip with friends.
• pxattr is a C++ module which enables the portable use of extended file attributes under Linux, FreeBSD and Mac OS X, by providing a uniform interface to hide the incompatible system calls.
• Sqlscreens is a QBE screen generator for SQL databases (mainly MySQL, but it has ODBC support). Written in TCL/TK and free. Also runs under Windows with ODBC, using Tclodbc, and it's a pure TCL/TK package then (no C needed).
• Writemime is a C++ module allowing building MIME mail messages (possibly with multiple parts and attached files) from a program..
• psxtcl may interest you if you want to hook up your pc to the real world.