I was just over in the DevonThink forums looking for applescripts that will capture pages and web archives from OmniWeb and put them into DevonThink (they have similar scripts for Safari). According to DevonThinks main developer:
I've just checked the latest build of OmniWeb 5.5 - it's still not possible to get the source or web archive of a browser or tab via AppleScript.
Is that something you would think of adding to OW 5.5? Thanks.
DougRay