+1  A: 

You might try umlet.com

Kindness,

Dan

Daniel Elliott
A: 

I find RFFlow to be very quick to start up, quick to learn and easy to use. It does diagnonal lines and text on slopes, and is good for block diagrams of all kinds. It saves as EMF and WMF as well as GIF and its native type, and copy-pastes into Word very nicely.

Martin