Account management system are web sites that let participants sign up for multiple projects with just a few clicks (and no account keys). The BOINC manager (version 5 minimum) lets you select, change, or get updated account info from an account manager.

Features include:
- register with BOINC projects without having to fill in all the same stuff again, it does that for you.
- manage resource shares for all projects from a single page.
- set per host what you want to run on it (attach/detach).

And probably more.