In an earlier article I listed the names of font families and the individual font names available on the iPhone. However, I didn’t take the extra step of actually generating samples of each font type. So here, thanks to some code published by Jonathan Saggau, is a composite image containing a sample of each font type, using the font’s name.
To obtain that font within your code, supply the given font name to the fontWithname class method eg.
UIFont *sampleFont = [UIFont fontWithName:@"MarkerFelt-Thin" size:14.0];
Ajnaware's Weblog 
THe list has been updated in the new version XCode http://www.myfirstiphoneapplication.com/2010/01/list-of-fonts-available-on-the-iphone/
THank you!!!! i just used this in my own iphone project and really appreciate it!
Excellent work Graham. I saw your earlier post on iOS fonts but wasn’t sure what most of these fonts looked like so was going to search for a font site to try each one out.. This saves a lot of time… Great work 😉