There are a number of programs out there that attempt to mimic QuickSilver for Windows and, at least, 1 for KDE (Katapult). Unfortunately, none of them quite live up to the standards that QuickSilver has set. It would be great to finally get something good for both of these platforms.
It would be really nice if the programs could directly access the indexes OS indexes, i.e. Vista index and Beagle index.