Out of town transportation ettiquette?

Unless it is a destination wedding, no.

I agree-- you shouldn't have to provide that.

We're not for our out-of-towners.

Talk to your hotel if you are getting a hotel block. Mine provided FREE shuttle service with 10 rooms booked. Yu can have the shuttle times posted in a "welcome letter" or on the "shuttle tickets" if the hotel wants them to have tickets to get on the shuttle. Again.. not saying you need to pay for one... but if one is available for free.....

Almost everyone at our wedding was an out-of-towner, and we asked people if they needed a ride from the airport. We ended up picking up only one guest--and even she could have taken public transit if we hadn't been available. Going from the accommodations to the ceremony, then to the reception, then back, we just asked guests who had rented cars to give rides to those who had not.

You absolutely don't need to provide transportation. But if you want to give guests some guidance, you could look into things like shuttles, public transit, or car-pooling among the venues.

If it's not in your budget, then don't worry about it. But I would suggest that you let them know ahead of time so they won't assume that you are paying for their transportation while they're in town. You could also put some "Welcome" packets together that not only includes directions to the wedding and reception, but also a list available forms of transportation that are available to them while they're in town along with contact numbers.