While I'm on hiatus from my pirates project, I was using a load of parts from the Wargames Factory WSS line (War of Spanish Succession).
Glancing at their new artillery kit, it looks like it has a ton of excellent 'Pirate' junk. Cannon barrels, boxes, spare cannon balls, and a bunch of figures which would look the part standing on deck, with a bit of imagination. Even some horsebound fellows for the port cities.
Worth a look, since they're dirt cheap by the box ($16 I'd guess on warstore)