Looking for simple 15mm scale rules.

[Dan55]

I second DBA.  A good game for small armies on a 2 x 2 board.

I modified the units somewhat to get a more colourful game.  You can check out some of the units I use at -

http://hardpointgames.netfirms.com/simplerules/dba4awi.html

[Paddy649]

For Ancients / Mediaeval DBA v3.0 is excellent. For Fantasy try HOTT.

[nic-e]

you could also try mighty armies. They say it's designed for 15mm on a 2x2 playing area and i find the rules light and fun.