Something that I have been working on with some people that I work with:
Benchmarking the HttpClient Caching Module
It was my first foray into submitting to an opensource project. I have had a lot of fun working with the team and with the Apache moderators in getting this into the 4.1 version of the HttpClient, which is in beta/RC currently. The caching client supports HTTP 1.1 response caching.
The beta can be found here: HttpClient Dev Site
If you use HttpClient - I encourage you to down load this new version and take a peek at the caching client. We would enjoy getting feedback on the usefulness of the tool and how it can be improved.