For a lot of tools I need, I generally manage to make a photoshop action or something to half way alleviate the repetitive dull tasks that take time away from drawing.
Recently I found myself needing to scale down a lot of tiles, with anti-aliasing - but no bleeding between tiles / over the grid lines. I thought I'd have to split my psd into individual tiles and then scale them all individually, but any tiles with transparency still had fuzzy edges after reszing. Pretty frustrating. Changing to 'bilinear' scaling seemed to fix it though, without needing to split it all up first.
Other interesting tools I've found and use:
Shoebox has a bunch of super useful tools in one package. (Extract unique tiles from screenshot, pack images to spritesheet, extract textures, all sorts of misc stuff.
http://renderhjs.net/shoebox/(I recently had to export 300 sprite parts from a PSD, again and again for a heap of colour variations, so instead I exported all once, packed a sprite sheet to apply the colour variations to, and unpacked the modified spritesheets. Saved countless of the dullest hours. Probably could have set things up better in advance, but it wasn't my PSD, so I had to work with how it was already set up).
I bought this on Steam, but haven't tried it yet:
http://autotilegen.com/Looks great for making all the variations needed for a full tileset.
Rotsprite for nice scaling/rotating of pixel art.
http://info.sonicretro.org/RotSpriteCurrently using Tiled as map editor. Pretty nice.
http://www.mapeditor.org/