Google's Code Search service can be used to search open source Curl code on the internet. To restrict your search to Curl files you can add the following to your search terms:

file:\.[dsmx]?curl$

Although, they don't (as of 8/14/2008) include Curl in their list of languages in the Advanced Code Search page, it does experimentally appear to work if you use:

lang:curl

instead of the file expression.

If you want your open source Curl project to be indexed by Google, you should explicitly submit it here to make sure it gets indexed sooner rather than later:

http://www.google.com/codesearch/addcode

Note that if you submit your Subversion repository, you should specify the non-authenticated http: path instead of the https: path, and probably use the path to your trunk branch.