I've been thinking about this for a while. What level of effort would be required to be able to specify all of the plugins that you want "bundled" then it pull the latest versions and automatically create a set of customized downloads (full,min,gzipped,etc)? It would allow you to have your one optimized js file instead of multiple files, or at least reduce the hassled of either putting them in the same file or including them only when needed.
I understand that there are some technical issues like not all plugins are officially hosted at the jQuery domain, but that could be the incentive for people to start using the jQuery site more as a repository. Additionally, you could create an account that would remember what packages you downloaded last, then email you when newer versions were available. That could even be a feature for "premium accounts" that were available for a reasonable fee...I know I would definitely sign up for it if it was implemented properly. Thoughts?