astable multivibrator, asymetrical multivibrator, complementary multivibrator, series multivibrator, emitter coupled multivibrator and more
http://www.4qdtec.com/mvibs.html
This circuit can be built with a single IC, two capacitors, three resistors, two trim-pots, and a diode.
http://www.elexp.com/t_oscill.htm
http://ourworld.compuserve.com/homepages/Bill_Bowden/page12.htm#flipflop.gif
astable multivibrator using discrete parts
http://www.repairfaq.org/REPAIR/F_samschem.html#SAMSCHEM_040