another very simple audio preamp to build. all parts should be available at your very local electronics shop
http://www.reconnsworld.com/audio_singleicpreamp.html
Simple Audio Pre-Amplifier using 2N3904. Provides good gain to week audio signal.
http://www.uoguelph.ca/~antoon/circ/preamp.htm
Uses Op Amp Labs modules 425
http://www.opamplabs.com/5hmaghd.htm
Designed for switching between harmonica mics. Includes low noise preamp
http://www.freeinfosociety.com/electronics/schemview.php?id=349
this is a very easy circuit to build - all parts can be found at the local electronics shop - no matter how worthless it (the local shop,) usually is..
http://www.reconnsworld.com/audio_simplepreamp.html
National Semiconductor Application Note. Chopper amplifiers have long been known to offer the lowest possible DC drift.
http://www.national.com/an/AN/AN-79.pdf