I've been designing websites for just over 10 years now (wow!), when my eighth-grade classmate introduced me to Geocities. I quickly taught myself HTML by coding using Notepad, and to this day I have yet to find a WYSIWYG editor that trumps Notepad (though I do use the Compose window for Blogger for the most part).
Anyway, while I don't consider myself much of an expert in XML, XHTML, or CSS, I must admit I was flabbergasted when I found out the code to open all links in a website in a new window was just simple HTML.
Since as of yet, nobody has answered my question of whether or not you guys prefer me to set all links to open in new windows, or for you to make that choice yourself, I decided to follow my gut instinct and go with the former.
Since Blogger couldn't be arsed to add an option to make all outgoing links open in new windows (I still highly recommend Blogger do that, though!), I was having to edit the link html every time to add a target="_blank" tag to open in a new window. It's the only thing that was causing me to jump into the Edit Html tab to get into the code. There had to be a better way, which meant a trip to Google.
Without further ado, here's the one line of code you need to insert to set all links to open in a new window:
(replace the [ and ] with <>)
Just insert that within the [head][/head] tags, before the [body] tag, and you should be all set! You can edit the HTML layout of your blog and insert it and it should work (I know, it worked for me)