Smashing Magazine recently published an article on High-Quality Free Fonts early this year. Among the beauties they call out, I saw Open Sans by Steve Matteson. It looks quite a bit like Segoe which seems no surprise as Steve Matteson designed them both. And with Segoe being my favorite font these days, I couldn't resist the opportunity to see how they compared.
At first glance, it's very hard to tell them apart as you can see below.

Of course we'll take a closer look. If you want get a really detailed look, I placed PDFs of my comparison files on my Skydrive
https://skydrive.live.com/redir.aspx?cid=1ff099edb1c7ebfa&resid=1FF099EDB1C7EBFA!1940&parid=1FF099EDB1C7EBFA!1925


Segoe is in blue. Open sans in in red.
Capital J – Open Sans is distinguished by a J that descends. I don't see this very often on fonts.

Lowercase g – substantial differences

Number 1 – Open Sans is more like Segoe WP for this character

Most of the remaining letters *look* almost exactly the same but on closer inspection, you'll see small differences. None of them seem to be the exact same shape.





GET IT HERE
You can download the fonts locally or use it as a web font via Google.