Well, it looks good in the plethora of browsers I so enjoy putting sites through (Internet Explorer 6 and 7, Maxthon 2, Firefox 2, Opera 9, Netscape 9, and Lynx), and both the CSS and Markup validate, so there are a few major pluses right off. I'm impressed that you've got it valid even with the content pulled from other blogs/sites.
The design is great - clean and simple without being too stark. The colour scheme works well, too - the grey and white backgrounds compliment the oranges well, and the oranges and reds in the logo, text, and banner photograph look great together. It has a very... errr... RSS-ey(?) feel to it, which fits with the content - I like it.
Design-wise, the only thing I would change is the white-faded area with the "add your blog" text over the banner image. I wouldn't have it fade to white, as it does. I'd keep it a slightly transparent white all the way across - enough white so that the text is easy to read, but not so much so that it obscures the image itself. I don't dislike the way it is now, but personally I think it would look better that way.
Everything was easy to use - the navigation, the search box, the "Add Your Blog" form, the "Subscribe to Our RSS Feeds" page, and the Language page - and worked great. It might look a little more uniform if the Subscribe and Add Your Blog dialogues appeared the way the Language Selection did - on the page you are currently on, above the content - but it's not really necessary, as it works fine now. Its just a personal thing.
The "Set your language" option confused me a little. I figured out pretty quickly that it was to limit blog entries to ones made in a certain language, but at first I expected it to display the site in another language. You may want to add a note explaining what you are selecting a language for, to avoid confusion.
I noticed that some blog entries contained a <iJJ> tag, which displayed as just a tag. It didn't bother be a whole lot, but it might be something to look into.
Also, I'd consider making the [...] at the end of the post excerpts link to the full post. I realize the post titles already do that, but it would be nice (and sort of make sense) for the ellipsis to link too.
Other than those few things - which I'll admit are partly just personal preference and nitpicking - I couldn't find anything I didn't like. It works great, and looks great. Two thumbs up!
-Patrick J. B. Simmons | @hobbramble
"If I could give you one piece of advice to remember for the rest of your life, it would be this: when Patrick tells you to do something, do the opposite." - Nolan Ladewski