First things first: make absolutely sure that you aren't using any copyrighted materials, because lawsuits can be nasty! And do all the obvious things like including documentation, installation instructions, contact information, etc.
Secondly, you need to package your project into a nice archive format. This should be a zip file (not self-extracting), and should include a version number in the filename, so that people can easily tell when you upload a new release. If you have separate archives for source and binaries, you should use the djgpp convention of a 'b' suffix for the binary files, 's' for the sources, and 'd' for documentation.
Make sure that your archive will unzip cleanly on both LFN and non-LFN systems. This means using only 8.3 format lowercase filenames. Don't use pkzip, because it will convert all the names to uppercase, which looks very ugly if you install it with LFN enabled.
You should include a directory structure in your archive, so that if people just copy the entire contents of the SimTel djgpp tree into their djgpp directory and then run "unzip *.zip", it will install everything into a sensible place. If you want to fit in with the djgpp tree structure, this means that your package should install into a contrib/mypackage/ directory. If you think that your package might someday be used with different compilers, eg. Windows or Linux, you may prefer to place it in a subdirectory of the Allegro tree instead, for example allegro/mypackage/.
Your package should include a manifest file, which has the same name as the zip but with a .mft extension, and contains a list of all the files in the archive. This should install into the djgpp manifest directory, or for packages that need to work on other platforms as well, the root of your package directory. The manifest file can be automatically generated from the zip itself, for example the Allegro zipup.sh file uses:
echo "Generating allegro.mft..." unzip -Z1 $name.zip | sort > allegro/allegro.mft echo "allegro/allegro.mft" >> allegro/allegro.mft zip -9 $name.zip allegro/allegro.mft
Having prepared your zip file, fire up your favorite ftp client, go to ftp.delorie.com, log in as anonymous with your email address as the password, change to the incoming directory, and upload your file. Make sure that you've selected a binary mode transfer, and check the file sizes afterwards to check that the whole thing was transferred successfully.
Finally, send an email to dj@delorie.com telling him the name of the file you just uploaded, and ask him to move it across to the Allegro directory on SimTel. If this is a replacement for a previous version of the same package, tell him the names of any old files that can now be deleted, and give him a nice short (half-line) description of the package to go in the SimTel index.
Further reading: see the Uploading DJGPP files to Simtel.NET HOWTO by DJ Delorie himself.