Here is a 12 volt 100 watt DC to AC inverter with center-tapless transformer.
http://www.hobby-elec.org/e_ckt30.htm
most reverse engineered from commercial products
http://www.repairfaq.org/REPAIR/F_samschem.html#SAMSCHEM_008
This description of the inverter is preliminary and incomplete.
http://www.technology.niagarac.on.ca/people/mcsele/i2k.htm
12V DC to 110V 60 Hz AC, up to 200W continunous, square wave output.
http://www.repairfaq.org/REPAIR/F_samschem.html#SAMSCHEM_023
http://www.web-ee.com/Schematics/110VAC%20Inverter%20for%20Automobile/inverter.htm
12V DC to 110V AC
http://www.interq.or.jp/japan/se-inoue/e_ckt8.htm
uses a normal 120 to 6V stepdown transformer in reverse to step 12V to about 350V
http://www.aaroncake.net/circuits/flampdrv.htm
power a variety of small (50 w or less) HID lamps, fluorescent lamps up to about 40w, HeNe lasers, flashes/strobes, neon tubes etc., from a 12 V car or marine battery or medium-size gel cell.
http://members.tripod.com/~wvsp/light1.html