I totally agree, Mark's monitor is great for efficiently tracking individual DB's inside SQL. I get a little nervous modifying MSDB or running XP procedures so there is a little tweaking I may do there to isolate the security and data.

Tory, what is the open source system monitor you are using? I've been playing around with Perfmon logging directly to SQL, and building some of my own ASP.NET to tie the data together in web pages.

http://aaronsmyers.blogspot.com/2005/04/nlogger-update.html

If there is already something out there to help, by all means I'd like to give it a try. MOM is just too expensive to justify for most of our servers/applications.