EV: Veselka (very good choice but very popular as well)
The Smith (usually opens all the doors and windows)
Belcourt (pretty big patio area)
Five Points (nominally Noho, tiny patio area, great brunch)
Cafe Orlin...or is it Cafe Mogador that has that small recessed sidewalk area? I can never keep the two straight.
7A (never been but it's pretty popular and very very cheap)
Yuca Bar (food was only OK for dinner but my friend is addicted to the Yuca fries)
Pylos (they open the doors and windows when it's nice out, really underrated brunch spot)
Mudspot (OK food, they have a decent back garden)
Chinatown Brasserie (dim sum, technically Noho, lots of sidewalk seating)
Back Forty (they have a backyard garden IIRC)
Double Crown (great atmosphere, not too crowded, I think they just started outdoor seating, I'd call to confirm)
Absinthe (they have a back garden IIRC)
Sunburnt Cow (really popular because of their drink special though)
Spitzer's corner (they open all the windows and the sill becomes seating)
The sidewalks are narrower on the LES so I don't think sidewalk seating is that common, that said, I did see Thor with all the doors and windows open and some seats last weekend.
"Cafe Orlin...or is it Cafe Mogador that has that small recessed sidewalk area? I can never keep the two straight."
Mogador. Not sure whether Orlin has any outdoor seating, but Mogador does have a few small tables outdoors, as you described.
I went to 7A ages ago, and found it totally underwhelming and not worth talking about at all. Another place with a different profile that's also popular and in two visits, amounted to nothing worth thinking about, as far as I was concerned, is Virage. (By the way, they also have outdoor seating, just for the record.) Just to clarify: Neither of these places sucked; it's just that in some instances, food just takes up stomach space and has no other function, if you get my meaning.
I think what 7A and Virage have in common is that their sidewalk patios are conveniently located right on the corner of 7th Street and Avenue A and 2nd Avenue respectively. Location, location, location.
I've been to Virage a few times before, it's merely OK, especially in comparison to other places in the neighborhood.