Run Xcode tools from the Terminal window
I'm using Snow Leopard + Xcode, and xcodebuild and xcrun are both present at /usr/bin. Regardless, they should be present at /Developer/usr/bin -- you just have to make sure that path is in your $PATH variable. You can set it in your shell configuration file (~/.bashrc for bash) like so:
export PATH="/Developer/usr/bin:${PATH}"As for the difference between sh and bash, bash supports some extensions and other features not found in the more primitive sh; however, on Mac OS X, sh and bash are the same program (this is typical on many Unix and Linux systems nowadays). However, when bash is invoked as sh (that is, you call /bin/sh from the command line, rather than /bin/bash), bash will try to act like the more "traditional" sh program.