What Visio Alternatives For The Mac Are There?

I needs a mac compatible UML diagramming application, and on the cheap is better. I've tried Gliffy.com as an online application, but I need something for offline use as well. Any suggestions would be great.

From stackoverflow

• Dia is always a favorite.

  http://projects.gnome.org/dia/

• Dia: http://live.gnome.org/Dia

  OS X port is here: http://dia.darwinports.com/

  I have not used it on OS X but it does exist...

• I'm a fan of OmniGraffle.

• OmniGraffle - $100 so not exactly cheap

  Some people use Adobe Fireworks although it's not exactly a replacement for Visio. Fireworks isn't very cheap either.

  Dana : $100! They've raised the price. I'm pretty sure I bought my copy in the summer for $70 or $80.

• According to 11 Free And Useful Open-Source Alternatives For Designers at Smashing Apps, Open Office Draw is an open source alternative to Visio.

• NetBeans has an UML modeller

  You can install the light version of NetBeans(the one with only Java support) and then install the packages needed from within NetBeans.

  This one looks nice too, cross-platform: yEd - Graph Editor