Signal Generator

There are some transmitters built specifically for this
purpose, often used in tracking payloads in balloons and
model rockets.

http://www.bigredbee.com/beeline.htm
http://www.silcom.com/~pelican2/PicoDopp/MICROHUNT.htm

or this:

http://www.rain.org/~marvin/microhnt.htm

You can use the PICCON controller with any transmitter to
provide keying and ID:

http://www.qsl.net/n6bg/piccon/

For a small, low-powered 2m transmitter with crystal control
try this:

http://home.att.net/~jleggio/projects/rdf/40mw_tx.htm

or:

http://home.att.net/~jleggio/projects/rdf/750mw_tx.htm

A frequency-agile transmitter paired with the Montreal
Controler (as well as the controller itself) is here:

http://www.qsl.net/ve2emm/pic-projects/mt525fox/mfx525-e.html

You can build your own transmitter quite easily: I've
used a scanner crystal on the 9th overtone, but now you
can get some pre-programmed crystal oscillators from
Digi-Key or Mouser for $6 or so. For example (just
because I had an old catalog handy) the Epson SG8002
series will only go up to 125 MHz, but you can order one
at 1/3 or 1/5 of the desired output frequency and extract
the desired output with a tuned circuit. Add an extra
stage of amplification if needed. You will need some
sort of controller for this, but the PICCON or Montreal
controllers will key it in CW.

For other ideas, try here:

http://www.rain.org/~marvin/equip.htm
http://members.aol.com/homingin/links.html