Christian Cantrell blogged an interesting peice on the use of target="_blank" this morning. Im not gonna echo what he says, and ive already left my thoughts there amongst the everyone elses comments. But one thing that i've just remembered reading at the begining of the year is that the W3C remondation for XHTML(strict) no longer include "Target" in the tag. What does this mean if you want to keep your document validated? you're gonna need to use Js. There's a complete article about this over at Sitepoint.com called New-Window Links in a Standards-Compliant World by Kevin Yank which explains more and the technique to open new window.

Also on Cantrell's blog there's a comment by Matt Shobe (near the bottom, posted at November 26, 2003 10:48 AM) about different styles for different links ("solid underline = new topic in existing window while dotted underline = popup window"), as seen in Microsoft viewer App. Personally I like, its simple and easy to understand, obviously some issues with Images etc, but for general text i think this would work well.