Well there are quite a few, you will have to try a few out and see what one will best fit your drawing style.
LT Spice »www.linear.com/designtools/softw ··· oftware/
TinyCad »sourceforge.net/apps/mediawiki/t ··· =TinyCAD
Solid Edge »www.plm.automation.siemens.com/e ··· /free2d/
Search for "schematic capture software freeware" for more.