I've been direct messaged on Twitter a few times by people wanting to know how to set up Twhirl to send tweets to Jaiku properly. They've already got Pownce set up just fine with their username and password, but their messages aren't getting through to Jaiku.
The problem is, unlike the Pownce password field, Jaiku needs your API key, not your password. To find out what your API key is, login to Jaiku and click the
API link at the bottom of the page. The page that appears will have your API key.
Enter your Jaiku username and the API key into the two text boxes in Twhirl, then enjoy having your tweets appearing on more than one site! This means you can keep in touch with people on three separate services, plus it makes you look like you're putting even more effort into your Web 8.0 life, or whatever version the 1337 media people have decided to assign to the intertubes now.