ecoShuttle

All in all, a highly recommended service if you are going to have transportation for your guests. Our wedding was about 40 minutes outside of Portland, so this was important for us. Their pricing was competitive (beat the pants off of some competitors, actually), and their drivers were very courteous. The give you water on the shuttles, or you are welcome to bring your own beverages.
We rented 3 vehicles from them on the day of our wedding - a 25 and 31 passenger vehicle, and a 48 passenger school bus. The 31 passenger vehicle actually had some issues getting up a fairly steep grade to our wedding site and the engine started to overheat, but they took care of that right away and all of our guests were still provided for.
We did some searching, and EcoShuttle was quite affordable compared to some other competitors, there were no hidden costs, we appreciated the bio-diesel vehicles, and Jesse Yun (owner?) was very easy to work with. Not everyone gets transportation for their guests as it's not always necessary, but if you go this route, I would highly recommend working with EcoShuttle - they will work within your budget

Using Eco Shuttle was an affordable and eco-friendly choice that worked out really well for us. The church and the reception were about eight blocks away, which might be too long for women in high heels or our older guests, so we decided to get a shuttle. Wanting to use something that wouldn’t be a total waste of gas, and wouldn’t break the budget, we chose to use the Eco-Shuttle van, which went back and forth between the two venues several times to get all of the guests safely to their destination (it ended up being a wee bit chilly, too, so just about everyone took the shuttle). On its last trip, it picked up the wedding party and photographers and took us to a scenic spot for pictures, and waited for us there, even though that trip took us just a little bit over our allotted time. They are a great company to work with and proved that they were willing to go the extra mile to make our experience great.