Some tools that can be used with Vim:

blink.c:C program to make the cursor blink in an xterm.

ccfilter*:C program to filter the output of a few compilers to a common
QuickFix format.

efm_filter.*:Perl script to filter compiler messages to QuickFix format.

efm_perl.pl:Perl script to filter error messages from the Perl interpreter
for use with Vim quickfix mode.

mve.*Awk script to filter error messages to QuickFix format.

pltags.pl:Perl script to create a tags file from Perl scripts.

ref:Shell script for the K command.

shtags.*:Perl script to create a tags file from a shell script.

tcltags:Shell + Awk script to create a tags file from a TCL file.

vim132:Shell script to edit in 132 column mode on vt100 compatible
terminals.

vimm:Shell script to start Vim on a DEC terminal with mouse
enabled.

vimspell.*:Shell script for highlighting spelling mistakes.

xcmdsrv_client.c:  Example for a client program that communicates with a Vim
   server through the X-Windows interface.

[xxd (and tee for OS/2) can be found in the src directory]