Ok, so we've got a dozen different systems, all with different databases and usernames and stuff.

So users have to login sys1.com an sys2.com and sysC.com and bert5.com all individually, with different (obscure) usernames and different password requirements (which expire on different schedules).

I want to create something so they can goto syslogin.com and authenticate once, with an obvious username (their email) and a consistent secure password policy, and then be automatically logged in to all the others without entering other details.

I think this is OAuth, but I can't find a useful explanation of OAuth, nor any practical examples or basically anything helpful at all.

Anyone done this before and able to provide any help?