Adorama is having a nice sale this week on Nils Kokemohr's famous Nik Sharpener Pro 3.0 (normally $199), the granddaddy of sharpening plugins. The boxed version works with Photoshop and Aperture, and ownership entitles you to a free Lightroom-compatible update. Nik Sharpener Pro is especially useful for digital printmakers, as it provides output-device-specific soft proofing. Another nifty feature is that you can specify a color range to be sharpened, leaving other colors alone. (I'm a big fan of selective sharpening, as you might imagine if you're aware of my involvement with the whole "bokeh" thing....)
It's probably worth getting the boxed version as the downloads from the Nik site are reputed to be on the slow side.
Featured Comment by William: "Oooh! I was just ranting elsewhere on the internet about how sharpening should either be a) final stage output specific or b) selective on signal features. My current hatred for the indiscriminate post-demosaic omni-directional difference kernel knows no bounds."