I don't use "diaper bags", and very much agree with siobhang about the colors. Pastel pinks and blues. Pooh bear and tigger. Baby Micky mouse.

I get regular bags that are very large. Or either sometimes trendy teenage school messenger bags are really up my alley.
I throw in a peice of felted wool sweater cut as a diaper pad to lay baby down on. And I make (or purchase, depending on what kind of waterproof pouches I can find in the store) a wet bag to throw in there to put wet cloth diapers in.
I like it if my bag has a place for a cell phone, but if not I just toss it in somewhere.
I just have an umbrella stroller for my little one right now. Before that I wore him all the time either in a mei tai or a sling, and used my stroller to cart around groceries. My only requirement for a good stroller is being able to push/turn it with one hand, I like that kind. Mine was like that, and it was so easy to push around. And maybe, that they recline in case I need to put munchkin down when sleeping (he was extra heavy when he slept) or add extra bags in. Other than that, I'm not picky about strollers.
OH! And also, here lately, it's been really important to have a bag large enough for my kid's potty ring. He's kinda scared of big bad public toilets, and I"m trying to use his potty ring to help him feel better. Hasn't worked yet so for though.
