Any suggestions for user management to allow bridging between web apps which would allow an adimn to set [ or users to request] different permissions for users per app? one username and pswd able to log in once and access various apps at various levels of involvement?

I don't fully understand what you're looking for, but if you want users to access multiple services without having relogin you might want to look into CAS (Central Authentication Service).

I have no personal experience with setting up CAS, but you MAY be able to pass data through the service to the application allowing you to preserve permissions. Don't quote me on that though.

Elaboration may help us determine what you should look into!

Maybe use openid or oauth from facebook, twitter, google, etc...

Unless web applications themselves support such a level of integration, it would be impossible.

Many apps support LDAP or RADIUS authentication. Don't know if the ones kjb is interested in do.