Alternative to Balsamiq for wireframing?

We keep a list of all the wireframing tools we know about here: <a href="http://www.twitter.com/balsamiq/wireframing-tools" rel="nofollow">http://www.twitter.com/balsamiq/wireframing-tools</a><p>Hope you find the perfect tool for your needs! :)<p>Peldi

I'm more and more addict to mockingbird (<a href="http://gomockingbird.com" rel="nofollow">http://gomockingbird.com</a>). It is still "beta" and lacks some features, but it is a really promising HTML5 application.

Not quite a "tool" but if you know basic HTML/CSS, you might consider using PolyPage with some CSS framework (like Blueprint)<p><a href="http://wireframes.linowski.ca/2009/01/state-based-html-wireframes-with-polypage/" rel="nofollow">http://wireframes.linowski.ca/2009/01/state-based-html-wiref...</a>

For iPhone wireframes, I've found <a href="http://iphonemockup.lkmc.ch/" rel="nofollow">http://iphonemockup.lkmc.ch/</a> to be a good alternative.

There is Pencil, which is either a stand-alone or Firefox addon. It's potentially good enough for a lot of things. Opensource too.