Crazy Browser and Firefox supports a custom list of external tools. Currently IE allows very limited support for this eg. addition to the basic list of programs for email, news, and editing. Currently, to edit the list of external tools you often need to use a registry hack. IE should allow you to set custom executables as external tools in the Internet Options dialog. This would let me use lots of automated tools that are command-line driven.
And please make it consistent with Visual Studio.NET Tools External Tools.