Windows users have the luxury of being able to load a flash drive with specially-modified "portable" applications, which run and keep all data contained on the flash drive so that moving them from computer to computer doesn't change the experience or modify the host computer at all. In the past I have gotten various apps from portableapps.com for this purpose.
Now that I'm a Mac owner, I wonder, is there an equivalent for Mac? At first thought I figured applications could just be copied from the Applications folder onto a drive, since they are self-contained; but I do know a little bit about how they actually store preferences in other directories and some even store things in the Library folder and stuff like that. So applications aren't truly natively portable, even if they require no installation.
Are there any portable Mac apps out there? Are there some recommended websites for these apps?