NSIS - http://www.nullsoft.com/free/nsis/
There are 6 things I like about NSIS : it's light, fast, computer friendly, powerfull, opensource and it's improved all the time.
OK, let's talk about NSIS. I was reading the docs recently and I'm considering using NSIS for future distribution of WME DevKit (instead of InnoSetup). Although I like InnoSetup and I still think it's pretty cool, there's one thing that troubles me - the distribution package size. The problem is, there's lot of graphics in the WME DevKit (templates, demos). Some images are duplicated (or even triplicated). What I need is an equivalent of WinRar's "solid" archiving, i.e. all the files are compressed "together", using one compression dictionary. This will reduce the distribution size A LOT. From what I've read in the NSIS documentation, it's capable of this (I didn't test it though; I hope I'm not wrong).
Plus, NSIS installers look cool (just look at the Dreams installation).
Plus, NSIS s quite flexible due to the scripting language (I have to say, though, that I really don't like the language, it's pretty weird