I put 500+: I have a Pathfinder sub, and I'll picking up all their new game stuff. I'm also assuming StarWars stuff fits here, and I'll be picking up all of those. Also will be picking up the occasional True20 product.
I voted $20-$100. I'll probably end up buying something at some stage during the year, probably a couple of Paizo adventures or something similar. If there are any big sales on the amount I spend could go above this. I don't have any specific planned purchases at this stage though.
I do plan on buying some Dungeons of Dread minis. They're technically 3.5E but I consider them to be more edition neutral. I might also buy some more Dungeon Tiles, which I think fit into the same category.
I have a ton of 3e/OGL stuff, more than enough to last me a lifetime. I expect I will get a ton more though as there is still a ton I want and that are at attractive price points for me.
I expect the majority of my monthly rpg budget to be spent on 3e/OGL stuff through 2009.
I expect I will buy some older edition D&D pdfs as well and the odd other system gaming pdfs if there are good sales (particularly Exalted and Werewolf the Forsaken) but the majority will solidly be 3e/OGL stuff. I don't expect any 4e stuff or WotC 3e pdfs to be at an attractive sales point for me however.
I already spent a bunch picking off the last of the d20 Goodman pdfs I wanted on Jan. 1 before they were permanently removed from sale.
I've got a bunch of Necromancer and AEG pdfs I'm eyeing for February, with OGL Game of Thrones and Amethyst calling out to me as well.