I agree with everyone... we use $1 store work books, reading books and many of the links listed. I printed and made a bunch of folder games from preschoolprintables.com and have also created my own. I have Early Education At Home by M. Jean Soyke, and love some of the ideas in there. I haven't used it "strictly" because my preschoolers will only be 3 and 2 the end of this month, but it is alot like letteroftheweek.com which I like too.
Just some words of advice: Keep it fun! Don't think you're being lax or lazy if you're not doing a pk curriculum with a 2 or 3 yo! Remember your children are going to be schooling for MANY years! LET THEM BE KIDS while they're so young! Don't feel you have to prove to others how intelligent your child is by having them learn all sorts of stuff by the time they're 3 or 4! I think ALL kids are geniuses! And they DO learn so much just by doing fun things! Let them do natural things: exploring outside, taking walks, etc. Remember, not long ago, even in our childhoods, noone would have EVER considered using a curriculum for pk! It's not required (at least not yet, though the government is trying to get kids away from home earlier and earlier!) or needed! Doing want parents naturally do--playing with their kids and letting the kids do games and puzzles and singing and counting some and reading aloud to them---that's more natural and they learn WELL with that!