It's part of a chain, but
Fadó is a short cab ride or reasonable walk in good weather from the Magnificent Mile (Michigan Avenue). Huge, fun and generally not as corporate as you would expect. Another option is
Kitty O'Shea's in the Chicago Hilton on South Michigan Avenue, although the prices there are rather high, the character of the place is quite pleasant and relatively low-key (the vibe is comparatively amped-up at Fadó). I'm sure some others here will post better options, mostly in far-flung neighborhoods, some of which might actually be worth the El ride, if you can make the time.
JiLS