Mail Act-On 1.3 is a Mail.App plugin that allows you to assign mail filters to keys. Additionally, there is a Quicksilver-like selection interface when you press a general hotkey.
The tool has a bug when used with a non-English version of Mail.app: when it tries to set the stop rule, it hangs. You can either create the stop rule manually (simply create a rule that starts with the same prefix as all other Act-On rules and set the action to stop rule processing) or disable the check for the stop rule in the settings - in the latter case, you should make sure that you have deactivated all Act-on rules, because otherwise they will also run on incoming emails if Act-On is not loaded for some reason - and they will cause all kinds of mischief with the emails.