EAW Sharpen is a filter which sharpens an image without annoying halos. It's based on Mikes Python plugin:
More info about the algorithm from Raanan Fattal:
To install the plugin, download and unzip the attachment, and type "make".
You will find the plugin then under Filters -> Enhance -> EAW Sharpen.
If you like it, hug someone :D
In the example image a strong sharpening has been applied with GIMP's Unsharp Mask and with EAW:
Update1: GRAY* and RGB* supported.
Update2: GUI updated.