FF II - Starting them out.

FF III - Not really sure what they did here

FFIV - Mostly transport, but could store items too.

FFV - Again, mostly transport, but where in the storyline more.

FFVI - Pretty much transport/excuse to show off better graphics :P

FFVII - A whole freaking subgame!

FFVIII - Not much really, unless you're Japanese.

FFIX - Subgame like FFVII, but had some story to it.

FFX - A few minigames later, but without the MAP, what's the point?!

FFXI - I don't know this one.

FFXII - Or this one.

FFXIII - ditto.

Any other FF games I haven't mentioned (including X-2)