If you are in the area, I like the atrium in the IBM building (~57/Madison). There are bajillion coffee shops you can easily find, all very crowded.

(or, if you are in NYC a short time, stop working! See NYC)

Besides the obvious Starbucks choice[1], my personal recommendation: PieFace. Their cafes are throughout midtown and have good coffee + outlets + seating + great food (Australian meat pies and pastries).

They claim to have wifi but I usually use my phone's hotspot.

1 - for those who want (need) Starbucks, the one at 39th and 8th Avenue has tons of room on the second floor seating area.

Thanks all for the recommendations. I also found the CapitalOne 360 cafe to be pretty nice on the second floor (bonus: TV for world cup games :)). Interest is a bit slow, but the area is nice. I'll check out the other recommendations. I'm also down to meet up, I'll be here until Wednesday (traveling from SF, where I worked at a Startup there)

NYPL on 42nd st and 5th ave. Free wifi and incredible architecture. Plenty of quiet spaces to use. Also a small coffee shop inside.

The Met museum's cafeteria. You have to pay to get in, but how much is up to you.