This is a recommendation for Katz's Bagels in Chelsea. I pick up their bagels whenever I get a chance. They are the closest to an NYC bagel you can get in Boston, better and more consistent I feel than Rosenfeld's in Newton. The bagels are also decent sized, not overly large, and are fairly priced at $3.35 a half dozen. I just ate half an egg bagel and it had wonderful flavor that reminded me a lot of St. Viateur Bagels from Montreal.
Katz's also makes by far the best bagel dog I've ever had. They tell me they use Vienna Beef hotdogs from Chicago. These are only $2 but they tend to run out.
They also make - and claim to have invented - pizza bagels. These are simply delicious half bagels with sauce and cheese. I think they're like $1.35 each.