There now appear to be quite a number of different search engines on the internet now that index open source code repositories and allow you to search them. Some of the more popular engines are Google code search, Koders, and Krugle. Unfortunately, non of these engines list Curl as a supported language or index any of the recent open source Curl projects. Update: Google Code does now appear to index Curl code, but still does not include it in their list of languages. You can restrict your search to Curl files by including the following in your query: file:\.[dmsx]?curl$
The best ways to change this situation are to make more user requests to those sites asking to support Curl and to create more open source Curl projects to index. So if this feature is important to you, consider visiting one or more of those sites (or if there is some other site you prefer, let us know in a comment) and request Curl support (or second an existing request). Here are some links:
Google Code Group
Koders feedback form
Krugle Forum: Feature Requests
And if you have some Curl coding projects sitting on your computer, why not go ahead and create an open source project so others can see what you are up to? If you do, we have found that both SourceForge and Google Code are good choices for free project hosting. SourceForge has been around a lot longer and is more fully featured, but makes you jump through more hoops. My own Zuzu project is hosted at Google, and I have been happy enough with it so far.
Update: since Google does appear to index Curl files, you should probably explicitly submit your repository to Google for indexing if you want it to show up:
http://www.google.com/codesearch/addcode
