Chop
   TAssembly Language program for splitting large files (up to 4GB) for easier distribution. Files can be split by either the number of files specified, the maximum file size, or use preset common sizes for floppies and CDs.
   http://www.sinnercomputing.com/Chop.htm

Goetz's File Splitter
   Split a large file into smaller files to fit on floppies or e-mail attachments. Command-line tool.
   http://www.lawrencegoetz.com/programs/gfsplit.htm

SplitIt!
   Macintosh freeware to split a file into pieces of any size then reassemble it.
   http://www.cs.utk.edu/~hedden/split.html

Splitpea
   Command-line tool written in Python that can split a file into multiple fixed-size pieces and join those pieces to form the original file. Runs on Linux and Windows. GPL from dOxxx.
   http://www.doxxx.net/