From left to right: Chimamanda Ngozi Adichie (Nigerian author: a VERY interesting TED talk she gave can be found here, I highly recommend it!), Palestinian graduate from An-Najah National University in West Bank, a young Edward Said, and artist Natascha Röösli.
Likeness is not very good in any sketch, though! :P
(The palestinian girl especially was VERY good looking. I ought to give it another go... )
Characters from Mass Effect 2. The first one kind of looks like a young version of my Shepard, but I did it off the top of my head, and didn't remember her features too well. I got some screenshots of her, though: At some point I'll draw her too, I guess.
Next is an unfinished one of Samara, and last is Garrus Vakarian.