Application for sketching ideas on a computer [closed]

Question

I've always wanted to sketch all ideas I come up with in the computer instead of on paper, but everyone knows that sketching with good 'ol fashioned pen and paper beats the crap out of trying to do it with a mouse (or even worse, a touch pad).

So I turn to stack overflow with this question: Does any one of you know a magic program that will help in sketching out diagrams, ideas, etc. with decent speed on a computer?

I'm not after something that will do pretty diagrams (that take ages to do, btw.) like Visio, Dia (kudos the the Dia developers though, kick ass app), etc. but for jotting down quick ideas and drawing early work flow sketches, etc.

(I know - a wacom board, but it's not really feasible to carry it around with your laptop)

Answer 1

I still go for a whiteboard and a decent camera on the mobile phone.

Normally when working on the whiteboard, we often go through a phase of erasing out all the unimportant stuff after we've worked out what the real essence of the problem and the solution. So we put some nice pictures on the wiki ;)