I am having a really hard time finding out the best, cheapest way to get from Montpellier to Marseille. I'm really confused with the train stations, if there's a bus option, etc. If anyone has any advice I'd appreciate it!
Rail pretty much has a monopoly for all but local travel in France. The main stations in those cities are Montpellier Saint Roch and Marseilles Saint Charles. Given the distance, you may want to book a cheap ticket on a fast train at www.tgv-europe.com (claim you live in the UK) in advance. Or you can get a cheaper ticket by slower train in Montpellier.
I can see and buy these tickets on www.tgv-europe.com. An English page will appear. On the upper right "Book Your Train Area", select Great Britain as your Ticket Collection County at the bottom of the area. If you select USA, the site will switch you to RailEurope which you don't want. Don't worry, you won't be visiting Great Britain. I can see fares as low as 15E. These fares are known as PREM fares and are both non-refundable and cannot be exchanged. But, they work quite well. If you are successful in buying your tickets on the website, you will receive and email and you can print out your tickets at home. This is why you won't need to visit Great Britain. Note that the 06:36 departure requires no train changes. This run takes just over 2hrs. Other runs will require at least 1 train change at Avignon. Some runs require 2 train changes. Run times also increase with the train changes.
Thanks so much for your help!