Aaron Hursman shares an example of his sketch-style wireframes using Jonathan Abbett's Sketch Stencils for Visio.
Thanks to Andrew for the link.
Sketchy Wireframes
Blog
UX Vision: The design superpower also known as The Squint Test
UX Hero points out a technique that you may not be using, but should consider. Stepping back and squinting to evaluate your work is something I was told to do repeatedly when I was first learning to paint, and is something I still do today as an interface designer. It helps you see the whole of your screen and look for anything that stands out, and see what needs to draw more attention, depending on the priority and hierarchy of your page elements.
It's certainly useful for visual designers, but can be just as useful for interface designers. Another thing I do related to this is zoom out and turn my wireframes into visual thumbnails on the screen.
Team Whiteboarding with Twiddla
Twiddla is an easy to use collaborative whiteboard service, but it's really got the potential to be much more. The whiteboard lets you mark up websites and graphics, and even use a drag-drop library of interface elements for working on interface concepts collaboratively. You communicate with others in the meeting with the chat window, and you can also use built in audio-conferencing capabilities. Very impressive, and free. Would make sense for there to be options for private meetings as well as embedding the whiteboard into your CMS or intranet.
I just gave it a try and the images they've provided are very restrictive. They're basically just graphics you drag in, but they can't be scaled outside of their original dimensions properly since they're bitmaps. It's also not a true prototyping environment like Balsamiq or iPlotz, since there are no properties for the elements. The best you can do is draw or even upload your own bitmap elements. It's truly only a whiteboard. That said, the drawing capabilities are decent.
To give it a try, click the Twiddla button: 