Hi Tina. The administrative assistants at my job use mostly Microsoft Office 2007. They use mainly Word for word processing, and are expected to be the gurus of all the tricks of the program and support the managers & technical staff. They also may use Excel, but never for anything complex that requires them to develop a lot of formulas, etc. It's mostly used for making lists or charts. They use Access databases, but they don't have to set them up. The forms are pretty easy to use once someone else generates them.
I think they also use Adobe Acrobat and a few other things occassionally.
The most complex stuff is probably using different project management and document control type programs. The good thing is no one is expected to know how to use these when they start, we train them.
As for training, at my company, if you weren't current in these programs, you would probably start as a clerk, who actually helps the administrative assistants with filing and other stuff. You would get exposed to the software and other responsibilities by helping someone experienced. Sometimes our company pays for training, like this year they sent all admins to a JuCo weeklong session for Office 2007. Our Junior College has "workplace enhancement" programs ongoing all year. You can sign up for noncredit classes. Some are all day, weeklong courses, others are one night/week or something.
If you aren't up to date on Office, I would highly recommend it if you want a position in a corporate environment.