You must be familiar with linux, and GCC compiler, here is the guide on building the toolchain for developing native apps for iPhone. I did it on VMware with fedora 7 on it..
1. http://code.google.com/p/iphone-dev/wiki/Building <---follow steps here, windows users can try it on CYGWIN, many people got it working but not me..
2. if you are getting stuck post error there or view by blog aakash-bapna.blogspot.com for problems i came across and there solution
3. You will need a decrypted,extracted iPhone image, may be some fixed symlinks in /usr/lib folder and MacOSX10.4u.SDK all these files are uploaded here- http://rapid$hare.com/users/JCFG2J
Post toolchain install--
* sample test app that worked for me http://absolutech.org/files/testApp.rar , extract, goto directory in terminal type make, place the no extension compiled file and info.plist in a Sample.app folder, transfer them to iPhone over SCP , set permissions to 0755. congrats you made your first iPhone app