In reply to Ciderslider:
Also at VS 4c is Plumb Line at Running Hill Pits - a *** jamming classic but not so well-known.
Central Crack at Wilton 3 (HVS 5a).
And the very well-known Flake Crack VS 4c at Helsby.
On several of the routes mentioned, like Bond Street and Dexterity, the jamming section is really the easy bit, with a harder crux where the jams disappear. Hen Cloud, as mentioned by others, and the Roaches also have a number of worthwhile crack climbs. When you think you've cracked it move on to Ramshaw and be humbled...
Of others mentioned:
- Saul's Crack: I suspect a lot of people layback the crux as it's very tight for my size of hands
- Hen Cloud Eliminate - another with a crux where jams disappear
- Roof Route (Rivelin) - no, no, no, a terrible experience
- Climbers Club Direct - yes, yes, yes, another classic
If you're based in the south you should really pay a visit to High Rocks - several classic crack climbs, like Coronation Crack, on rock that is more forgiving to the hands than gritstone.
Best of all in my experience for jamming cracks is Turkey Rocks but that's in Colorado!