I'd suggest finding your local SQL Server user's group or a virtual chapter on administration. Start by looking at www.sqlpass.org, the Professional Association for SQL Server. It's a nonprofit that runs a bunch of user groups and chapters and various free training events nationwide (SQL Saturday for example).
For specifics on SQL Server admin, the true path to mastery starts with understanding transaction logs, backups, and restores. Paul Randal (http://www.sqlskills.com/blogs/paul/) is the foremost expert on teaching such things, since he wrote a lot of it when he worked for Microsoft. He covers backups, recovery, transaction logs, troubleshooting, and general storage-end stuff. I've been doing SQL Server DBA work for almost 19 years, and his blog still teaches me things regularly.
As for Exchange, learn the basics of how Active Directory authentication works, how SMTP and IMAP work, and most importantly for any mail administration, how spam filters work and which ones are good and which aren't. Exchange is a complex system and I'm not as familiar with it as I used to be.
People (especially here) will tell you that Exchange is crap, which totally explains why millions of companies that are profitable use it, because it's crap. Oh wait. That's right, they use it because it works and provides value to their businesses. Perhaps they have logging requirements imposed on them by various regulations (SOX, for example) and they'd like to share the liability if something doesn't go right, have off-the-shelf commercially supported and legally recognized tools for discovery, and having that security blanket provides them with value for their business. If you go into an interview situation and they ask you about your Exchange experience and you start with "Exchange is crap, use Sendmail instead!" they'll thank you politely and walk you out.
As for anyone starting out in the tech field, especially on the admin side, I'll offer a few little bits of advice:
Keep things as simple as possible. It's usually cheaper in the short and long run to throw hardware at a problem than it is to build something elegant and hard to manage.
"Robust" doesn't mean it works all the time. Robust means it fails in predictable ways.
Centralized Logging + Morning Coffee means never having to tell your boss you don't know what broke overnight.
Checklists. Build them, use them, every time. Server builds. Software deployments. Backup procedures. Restore procedures.
Don't plan backups. Plan restores. Figure out how you want to recover from a backup, and then figure out how to do backups to support that.