If you use the "lunch 1" configuration, and build, the emulator will be built as well. The ". ./build/envsetup.sh" step that precedes "lunch 1" should also set up your environment so that the "emulator" binary is in your path and the Android-specific environment paths point to the built system images. However, you will still need to specify the kernel image on the command line.
Note that this process does not include the "Google Apps" in the emulator (one of the things the extract-files.sh script pulls from the the NexusOne). It's technically possible to extract them from an Android emulator include them, but I haven't done it personally. I imagine there is a HOWTO out there somewhere.
Thanks,
-Will
--
William Enck
PhD Candidate
Department of Computer Science and Engineering
The Pennsylvania State University
en...@cse.psu.edu