I know that there are some caching classes introduced in the iphone sdk recently, and there is also a TTURLRequest from three20\'s library that allows you to cache a request
I recently found this project under github :
http://github.com/rs/SDURLCache
The approach is quite the same as my previous answer described here How to save the content in UIWebView for faster loading on next launch? , but the code looks more polished so maybe it makes sense to give it a try.