For really long zoom, reviewers consistently put the Canon SX10 IS (20x, 28-560mm 35mm equivalent zoom) and Panasonic Lumix DMC-FZ28 (18x, 27-486mm) at the top of the pack. Both list for $400 in the States. Only the Canon has a hot shoe. Neither would fit into a pants pocket.
(The Panny was discontinued recently, though it can still be found. Its replacement, FZ35 in the States and FZ38 most other places, has been announced but isn't shipping yet. It's a non-trivial, but definitely not earth-shaking, upgrade. Few reviews so far. No hot shoe.)