I believe part of the strategy from Apple is that you OWN a Mac if you want to become a developer. I haven't checked the latest articles/details regarding their licensing system, but I know that Adobe is now able to ship Flash Builder 4.5 which generates code for the iPhone. I wonder if you still need a Mac to upload it to iTunes.
Xcode, the developer tool from Apple for iOS is Mac only.
There is another approach I've been told though. If you have a spare PC or harddrive, you can buy the original Mac OSX DVD (actually rather cheap last time I checked) and then with a lot of tweaking and researching, you can install Mac OSX ontop of PC hardware and have a dual boot machine.
Look on google for "hackintosh". Its not every PC that will work with this, but search, read and try - it ought to be possible. I am not sure what Apple thinks about this, but if you start by buying the original Mac OSX instead of using a pirated copy, I believe you should be "okay" - cant promise you anything, but thats what I've been told by someone who did it himself.