It took me a couple tries to get this, but it is really straight-forward. The trick is to drag the del.icio.us bookmarklet into the Safari toolbar on your computer; and then sync it with your phone. ITunes will place the bookmarklet on your phone’s browser. To invoke it, simply select that bookmark while viewing a page and it opens the usual del.icio.us post form. Now, the cool type-ahead javascript doesn’t work but otherwise, you’re in business.