Slurp is a project mainly written in JavaScript, it's free.
Import del.icio.us bookmarks into Firefox 4
Slurp is a Firefox extension built using the Add-on SDK that lets you import your del.icio.us bookmarks into Firefox 4 (Go get the latest beta: http://firefox.com/beta/).
No restart required - just install the XPI and head to http://del.icio.us/
You can already export your bookmarks as a HTML file on del.icio.us, but importing that directly will not preserve your tags and notes. Slurp makes sure you don't lose data.
Once your bookmarks have been imported to Firefox, you can securely synchronize them and take your data wherever you go; thanks to Firefox Sync (http://firefox.com/sync/). You'll find them in the 'del.icio.us' directory in your bookmarks menu.
Give it a sip.