アドレスバーに検索機能を追加するKeywurlが遂にSnow Leopardに対応しました。

Snow Leopard support コメントを見る
Keywurl should now finally work on Snow Leopard in 64-bit mode, thanks to the brilliant work of Anthony Ramine and Dave Vasilevsky.

Note that the latest version of SIMBL, which is bundled with Keywurl, is required for this version to work on Snow Leopard in 64-bit mode. If you already have an older version of SIMBL installed you will need to reinstall SIMBL from this package.
Keywurl 1.4 beta 8 for Safari 4はMacOS X 10.5(Leopard)及び10.6(Snow Leopard)のみの対応となり、最新のSIMBLが必要となります。