Question: I am familiar with archiving messages on the client side to .pst's... Are there good methods of archiving messages from multiple mailboxes on the server side?

Answer: 
I recommend Barracuda's [Message Archiver](http://www.barracudanetworks.com/ns/products/archiver-features.php). It keeps a complete archive of all mail. It can also trim attachments from exchange and host them itself. It provides a link in the original message to the trimmed attachments.
I invite you to try out the [exchange archiving](http://www.metalogix.net/Products/Professional-Archive-Manager-for-Exchange/) software from Metalogix too. Priced right for small business and all the solutions we needed. Symantec was too complex and pricey for us. The company I work for had a problem where we couldn’t go to a hosted model for fear of privacy and clients wishes. We had to archive with something in house. Thx