So here's one idea:

An OpenID 2.0 Library, in C minor.

There are already a lot of implementations of OpenID, but none of them are done in C. Now this might not be the first language that comes to mind when one thinks about it implementing it, especially since OpenID is (at the moment?) mainly targeted at blog-style web sites, which are often programmed in languages like Ruby, Python, or Java.

But there might be just a target for a C implementation; it could be light-weight, and perhaps a little faster, though this would not be a design goal it could be plugged directly into webservers like lighttpd * it could be used as a basis to create libraries for other languages, since most languages seem to have C-hooks to create API's

For instance, what I'd like to see (i actually had a working version of this for OpenID 1.1, just never got around to polishing it up and releasing it, and now it's a bit stale, to say the least) is a plugin for lighttpd and/or apache, that uses OpenID as the underlying mechanism for http authentication.

When this is used instead of any http-auth modules, scripts and websites that rely on the authenticated-user value in the web server, don't have to be changed, and they can support OpenID.