I also heard of a NICE beer garden in Williamsburg:
http://www.radegasthall.com/
It's hipsterville there, but the place is supposed to be awesome!
Also, there is a cool Czech beer garden in Astoria, Queens. A bit out of the way, but it's nice in the summer. I've been there.
-Joe
Edit, beer list for this place (Radegast):
Blanche de Bruxelles Witbier BEL 7 13 18
BrouCzech CZE 7 13 18
Franziskaner Hefe-Weizen GER 7 13 18
Gaffel Kolsch GER 7 13 18
Gosser Pilsner AUT 7 13 18
Hofbrau Lager GER 7 13 18
Hofbrau Oktoberfest GER 7 13 18
Krusovice Imperial CZE 7 13 18
Palm Ale BEL 7 13 18
Radeberger GER 7 13 18
Spaten Oktoberfest GER 7 13 18
Weihenstephaner Dunkel Weisse
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Augustiner Brau Edelstoff GER 8
Barbar BEL 9
Bayerisher Banhoff Berliner Weisse GER 8
Buggenhout Kwak (Pauwel) BEL 8
Buggenhout Tripel Karmeliet BEL 9
D'Achoufe La Chouffe BEL 9
De Dolle Arabier BEL 9
DeKoninck Ale BEL 8
Dinkel Acker GER 7
Eggenberger Urbock GER 9
Einbecker Non-Alc. GER 7
Einbecker Ur-Bock GER 8
Floris Apple BEL 8
Franziskaner Hefe-Weizen GER 7
Fritz Briem 1809 GER 9
Gouden Carolus BEL 8
Gouden Carolus Tripel BEL 9
Green's Discovery Gluten Free BEL 9
Grimbergen Blonde BEL 8
Kasteel Rouge BEL 9
Koenigshoeven Dubbel NL 9
Konig Pilsener GER 7
Leipziger Gose GER 7
Lindeman's Pomme BEL 10
Lindemans Cassis BEL 10
Lindemans Framboise BEL 10
Lindemans Peche BEL 10
Malheur 10 BEL 8
Pinkus Ur-Pils GER 8
Regenboog Smisje Wostyntje BEL 8
Schlenkerla Helles GER 9
Schlenkerla Marzen Rauchbier GER 9
Schneider Aventinus GER 8
Schneider Edel-Weisse Organic GER 8
Spaten Optimator GER 8
St. Louis Kriek BEL 9
St.Bernardus Tripel BEL 9
Uerige Sticke GER 9
Urthel Samaranth BEL 10
Weihenstephaner Vitus GER 8
Westmalle Tripel BEL 10
Zatec (Saaz) Lager CZE 8
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You will feel right at home Felix...;-)
-Joe