It's just different flavors. Active Directory is easier on a Mac because it was designed to work with LDAP/Kerberos. AD is just an implementation of that in Microsoft land, although it causes problems by not being native to the system like NTLM, and of course has some proprietary extensions (embrace, extend, extinguish, the Microsoft way).
Instead of Exchange you have Mail Server. Or Snow Leopard is supposed to work seamlessly with Exchange.
Sharepoint. That's an interesting one. I haven't looked at other portal software lately.
SQL, of course there are many other database engines out there. The languages and datatypes are 90% the same, as are the larger concepts of management. It's just learning the differences of commands, best leveraging that platform's abilities, etc.
Visual Basic, what, are you high? Why are you still using that crap? :)
I’m assuming they taught us VB since it’s Microsoft, the Army’s School of Information Technology is an official Microsoft Academy, and it allows us to make custom front-end apps for Sharepoint. Although the rumor around the campfire is that we’re dropping VB for whatever reason (the jaded among us say it’s to prevent our own custom apps and making MS and other companies more money since we’ll have to buy THEIR software solutions...).