DeliciousToDelicious is a user script for posting to anything that implements the del.icio.us API using the del.icio.us posting interface. I use it to sync the bookmarks I post to del.icio.us with a local copy of Scuttle. It could also be used to post to two del.icio.us accounts at once.
A lot of the code comes straight from DeliciousToBlog, but this script's a lot simpler because the del.icio.us API is much less complex than the metaWeblog API.
Incidentally, I'd only find DeliciousToBlog useful if it provided some way to append new links to an existing post (so that I could include all of the day's links in one post, a la Tom Coates), but I'm not sure I'll get around to adding that.