No one has yet mentioned Sultan's Market (2521 N. Clark;
http://chicagofalafel.com/), which is a great cheap, fresh, and relatively healthy spot for middle eastern food.
Now, to be honest, since I live in Bucktown I've only been to the North Avenue location, which I believe to be the original location. However I do eat there several times a month and can vouch for consistant quality, freshness, and one of the best salad bars in town for the very low price.
$4 will get you very filling chicken schwarma pita (my fave), while the falafel is only $3. Both are a meal for me, but bigger appetites could add in a $2 lentil soup, one of their pies (egg/cheese; spinach; lamb?). The fettia (also $4, if memory serves) is quite tasty as well.
Point being, go there! I wish I could right now....
Hope this helps.