OD&D - mostly sticking to the 3 LBBs from 1974, with a dash of the supplements here and there. PCs are exploring my Dungeon23 creation.
AD&D/1e - continuation of my 14 year campaign. 3 separate groups in the same world, 1 is PbP, 2 are online (though one will go back to face-to-face in late summer)
Classic Traveller - just the 3 LBBs from 1977, in a mashup of Battlestar Galactica 1978 and 2003 TV series. No 3rd Imperium elements.
My style? I like to focus on roleplay and put the mechanics behind the screen as much as possible, though AD&D tends to not support that. But I try. OD&D/CT77 definitely promote that style of play.