Here's code I've used in various projects it's all released under the LGPL.

C

C++

Python

linked list (header)	threadsafe table (header) (example) (docs)
pthread wrapper classes (header)
base64 codec (header)	URL encoder
"Fire and forget" version of system()
get MAC adress of interface on Linux
libglade
dir_patt
subProcess (I got a free book for this. Thanks O'Reilly!)
human
utility macros and defines	High level socket functions (header)
bit operations macros
debugging trace (header)
variable size string buffer (header)
wrapper to simplify libcrypto interface (header)
string search & replace function (header)