Robert Huttinger has started what will eventually be a nine part series of videos in which he explains how to use an iPhone or an iPod touch as a universal remote. The videos are posted on YouTube.
Part 1 of 9: http://www.youtube.com/watch?v=R27d5XYHXC0
Part 2 of 9: http://www.youtube.com/watch?v=Vbl6C5hH5R4
Part 3 of 9: http://www.youtube.com/watch?v=u25E-53tyDA
Part 4 of 9: http://www.youtube.com/watch?v=Fn4kvhpQIDc
Part 5 of 9: http://www.youtube.com/watch?v=uDXRgJlAtm8
Part 6 of 9: http://www.youtube.com/watch?v=kKyIaKN-cbA
Part 7 of 9: http://www.youtube.com/watch?v=uqEJsmGmNUg
More to come...