I was at the Gilbane Boston conference over the last couple days. For all the right reasons, the new Gliffy plugin for Confluence received a lot of attention from anyone who stopped by the booth.
Techrigy has blogged about it as well:

I figured I would post today about Gliffy (http://www.gliffy.com) since I just finished using it and found the experience great! It’s not the first time I’ve used it and honestly, it makes perfect sense. If you haven’t checked it out, it’s Visio-like but free and with no install.

Note: Gliffy is offering a free 30-day trial of the Confluence plugin. Pricing is listed on their site, too.

“Try out Gliffy”...