There are some interesting TiddlyWikis available now that implement GTD-style todo list management, for example accela.net/~dankna/tiddlywiki/). This plugin also works with DT’s WebKit-based html display.
Tiddlywiki documents can be indexed by DT and appear in the DT database. If they are indexed only and not imported, they display in the DT html viewer but retain their functionality and save data to their location on disk (assuming that the plugin mentioned above is installed in ~/Library/Internet Plug-Ins). So the Tiddlywiki document can be used from within DT to manage the multiple views of todo lists (something that’s still awkward in DT), while the DT database can provide folders for the GTD Inbox, Read/Review, project support files and reference.