for msn you need to install account-plugin-butterfly from extra-testing.

(warning: software is extra-testing is still in a beta stage and not ready for end users. it can be buggy and even cause data loss. it is not recommended for users unfamiliar with maemo)

that said, the msn pluggin seems relatively stable. have been using it for a week or so. for other services, i would like to find out how to enable them too.