I'm new to the iPhone, first thing I did was try to find a PDF reader. The first one I came across is called 'Papers' (
http://mekentosj.com/papers/iphone/), originally designed for PDF describing scientific research, but works OK for any PDF that I've tried so far.
Nice features: it remembers your current position, let's you rotate, add bookmarks, and seems to be quite a nice 'library' solution (you can organize PDFs into folders etc.). Also, it syncs quite nicely if you also have the version of Papers running on a Mac.
Not perfect yet: once you close a PDF, it currently forgets your last position. This is really annoying to me, I asked the developers to fix it, hope they will soon. Also, it is quite pricey ($14.99) - even more so if you buy the Mac version as well.
Overall an interesting option - I would be curious to hear about other's experience with Papers, particularly if someone can comment on how it compares with other solutions.