Last year, I noticed my windows weren't perfectly draft sealed, especially in the middle (two part sliding window).
So for the coming winter, I will seal around the window trims and the center.
However, I find the price of weatherstripping (sticky foam tape) to be abusive for something that is thrown out every year. There are cheap rolls (cheap per foot) but those aren't wide enough to cover the frame's inside edge, since it's wider to allow the windows to slide.
Do you guys buy your supplies online/ebay? Do you use another product, like some sort of construction tape, that's cheap per foot that does the same job? (I think weatherstripping foam tapes are overpriced as they are marketed towards non-DIYers).
I'd use tuck tape, but the color... my wife would veto.