Until the Celtics ended the long drought for the Garden's resident teams, there wasn't much cause for hanging around the arena to throw back beers. But with the C's generating excitement the likes of which haven't been seen since Larry Bird hung up his mustache, Canal Street was reborn this yearand so, too, was the Fours. It's not as big as some other venues, and that's what makes it so appealing: squeezing elbow-to-elbow into a crush of like-minded revelers, Sam Adams in hand, throatily cheering on the local boys. There isn't another bar in town this good at producing the we're-all-in-it-together spirit. And since the Fours carries the major sports packages on more than 40 strategically placed televisions, no neck-craning is required to watch the game.