Well, most of that should be fairly easy to accomplish.
1. There are LOTS of good jabber clients for Linux. My personal favorite is GAIM (http://gaim.sf.net
). Another good client is PSI (http://psi.affinix.com
2. Connecting to an Exchange Server might be possible with the free Microsoft Exchange connector that can be used with Novell/GNOME Evolution. Information on this is availible here
3. Cisco does make a Linux version of their VPN Client. But, it can be hard to get a hold of. You might want to talk to your network administrator to obtain a copy. One thing to remember is that it is Console-based (no Graphic Interface at all). So, it may take a little getting use to.
Hope that helps.