It's a question that has bedevilled so many designers showing a wireframe to a client or member of their own management team, that it has become an an almost Dilbert-esque cliche. After loudly intoning: "it's a rough - take no notice of the fonts or the colours", they cautiously pop something on the screen, only to find that soon enough the debate turns to - the fonts and colours.
It's too easy to make jokes about pointy-haired bosses at this stage, but the simple truth is, that most wireframes, created in tools such as Photoshop, Visio, even Powerpoint or Omnigraffle (linked because this a personal favourite) have enough polish to override the designer's verbal warnings: The human brain is very bad at ignoring things.
And it is not just non-tech management fall prey to the problem. Designers do too. I've had conversations with Information Architects in the past who have sketched out ideas for a site or interface design, only to find the designer (who is meant to be the expert) has followed the sketch altogether too slavishly.
In 2002 veteran information architecture and user experience designer Dan Brown, came up with the idea of the Page Description Diagram, an attempt to describe, in pure text the hierarchy of elements on a Web page and how they work together. An excellent idea, but one that its rarely seen in the wild.
Which is why Balsamiq mockups, is such a breath of fresh air. This is a specialised graphical tool for mocking up user interfaces and Web pages. It gives you the pre-built wireframe elements, lets you drag, drop and resize and is smart enough to to know that (for example) radio buttons can have two states and to let you simply type in the labels for tab-bars and choose the one that should appear selected. It takes away much of the grunt-work.

Written in Adobe AIR, this is a young app, and it it wasn't the snappiest in the world to begin with. But over the the last couple of months, it's extremely responsive developer Giacomo 'Peldi' Guilizzoni has cranked out the point-revisions in response to an enthusiastic user community posting enhancement ideas and bug notifications on the company's Get Satisfaction page. A one-man-band, Guilizzoni is making himself a text-book case of how to use online tools to interact with your customers.
Mockups isn't perfect - mainly, I suspect because of the quirks in AIR. On Mac OS X OS's native keyboard shortcut don't always work, for example and performance still leaves something to be desired. Nonetheless it is the quickest way that I have found to put an interface together. Moreover, alongside its standalone, desktop version, there versions available as plug-ins for Confluence, JIRA and (in development) Twiki. In other words it slots right into your collaborative workflow system.
But one place where the software scores is the output looks truly rough. And I say that as if it is a good thing - because it is. There is no way that this can be mistaken for anything other than a mock-up. The font even defaults to comic sans, for goodness sake.
Some architects/designers might feel that have is that the results look a bit amateurish, indeed they might be a bit embarrassed to put this in-front of a client. Trust me: if you carefully explain the issues and why you are using a tool that enables fast iterations of new layout possible, while also making the rough nature of the layout explicit, they are likely to 'get it'. Indeed the first client I showed it to ended up getting a licence. It is far better to undergo a little bit of pain at the start of the process, rather than endure misunderstandings throughout the project.