I'll second the recommendations for Burger Joint (A+), Pam Real Thai (A+), and Afghan Kebab House (A-). A lot of the other Thai places aren't that good, although I've heard Wondee Siam is good (haven't tried it).

A few other inexpensive Hell's Kitchen recommendations:

• Ninth Ave Pizza just below 53rd is a personal favorite of mrsmicah's, although some people dislike the thyme he uses (my mom can't stand it). (A)
• Azuri Cafe on 51st just off 10th Ave is probably the best Israeli-style falafel joint in the city, served with a heaping dollop of attitude (think Soup Nazi, only without the sense of humor). (A+)
• Vynl is like a gay diner on acid (and I mean that in the best possible way--don't miss the themed bathrooms if you go). (A-)
• Meskerem on 47th just off 10th is a decent Ethiopian joint and is BYOB. (A-)
• Tehuitzingo on 10th just below 48th is a little Mexican bodega with a tasty taco stand hidden in the back. (A)
• Eatery at 53rd and 9th is a frou-frou diner. Kind of like Vynl but with a yuppie girl vibe to replace the kitsch. (A-)

There are plenty of other choices, too, if you wander up and down 9th Ave in the 40s and 50s.

Edited to add: As Analise mentioned, there are a million places in Midtown proper to grab a salad or sandwich for lunch that aren't Subway. You might also want to check out midtownlunch.com for some other options that are a little more hidden. For example, there's excellent Korean food in the back of Cafe Duke on 52nd between 6th and 7th (which otherwise looks like any other sandwich/salad deli). And some of the street carts are awesome, while others are downright terrible. My favorites are the Halal guys at 53rd and 6th (make sure you go to the southeast corner during the day, because the daytime cart on the southwest corner sucks), the Biryani cart at 46th and 6th and Kwik Meal at 45th and 6th. The Jamaican Dutchy cart on 51st between 6th and 7th is also pretty good, and the Schnitzel Truck (which is usually in Midtown on Mondays--see twitter.com/schnitzeltruck) is pretty good, too, although massively bad for you.