I've had a UX Stickynotes pad near me for a few weeks to play with. I'm kind of a sticky notes nerd. I mostly like to place them in sketchbooks to mark and annotate, but also like them for brainstorming and doing info organization exercises. Sticky notes for UI sketches and sketchboards makes sense.

The sticky notes are A5 sized, with light non-photo blue dot grid, and the browser version has 960gs markers. The adhesive is on the right side, which I didn't quite like at first, thinking it made more sense to put the adhesive on the top for white board/wall use. However, I ended up sticking them on the side of my MacBook Air while I was wireframing from a sketch, so that turned out to be pretty cool.

They have browser and iPhone sticky pads, and free templates as well. They ship from the UK.