Will they (specially Harrison who's out there as FA for a long time now) get to play in the NFL again? And most importantly: where?

I think both can still contribute a lot given all their experience. Probably not as the n1 option at WR, but certainly opposite to a young or a not so experienced WR.
In my opinion there's a long list of teams who could really use either of them.

Wake up Vikings!

marvin harrison was cut for money/salary cap reasons. i think he will resign for less money with the colts. his legal issues with shooting a guy will probably scare off most teams.

tory holt is still a good player. i think he could end up with the vikings, he would be the perfect compliment to bernard berrian.

Carolina doesn't have the required cap space. They said that. Well at least not until they send Peppers to New England.

Hmm. A team in need of a good WR who has cap space?

WAKE UP JAGS. You're one of few teams who need Holt that can afford him.

Another question is whether those guys will sign for any team or if they'll wait until a real contender comes after them.
Then again, given their age, maybe they can't be that picky.