Marc Hedlund over at the O´Reilly Network takes a look at the new bloglines web services and it´s advantages in helping solve the RSS overload problem by acting as a feed cache.
BTW, for providing client HTTP functionality in an application (including authentication) HTTPClient (for Java and Groovy (java based scripting language)) is recommended; while for Windows wget and cURL can be used (for application in PHP or whatever).
The article also mentions further ideas for using the Bloglines API, such as a RSS-to-mobile gateway (to strip out information not necessary for mobile devices/phones or simply to reduce bandwidth requirements).
Update: Another approach for feed caching is distributed checking, sort of checking RSS over a P2P network.