You could probably start here, with DaniWeb. At the top of each language forum is a tab for "Code Snippets". For example, the C++ forum has a tab within which you could create a thread posting your C++ code.
There are also two websites that come to mind quickly:
These two sites accept code submissions in a variety of languages for many applications.
Also, there are the freeware sites (I mentioned already), and many scripts sites. Check out the list below. Many of these sites call themselves scripts sites, but they also accept a whole range of code submissions.
Finally, I suppose you could post your programs as projects on sites like sourceforge, fresh meat, Google Code Project, etc. A search for open source software or open source projects should turn up many more.