Usernames across Applications

Hello everyone, I was just wondering if there was a way to make it so that usernames could be used across applications.

For instance, I have a server that has a bunch of users. I want these users to have ways of accessing my database as well as a variety of other programs, but I don't want them to have to remember, or even have to set, a huge number of passwords.

Any help is greatly appreciated. Thank you.

These 3 are prefered way of doing in order of preference.

ahhhhh DUH

LDAP....DUH

I knew this and I didn't even think! Thank you.