ONCF run both the railway and the Supratours bus service, If you buy a ticket from Cassablanca to Agadir or vice versa, you will travel by train and bus changing in Marrakech.
Its not a bad journey but it takes all day. both the train and bus service in Morocco are reliable, clean and comfortable. Snacks and drinks are available on the train and the busses make regular toilet stops.
I have used Abdou as a guide for my 1 day visit to Agadir, he used his car and drove my friends and I to Touradant which is his home town and gave us a personal tour and then drove us back to make a ships sail away that afternoon.
What I liked about Abdou is he's a genuinely nice guy, full of knowledge since this is his homeland, and he speaks perfect English~ I was surprised when he told me he did not learn in America.
Whether you have 1 day or more, or want to see other parts of Morocco, email Abdou and see how he can help you.
Buses leave Agadir from the Rue Yacoub El Mansour. Cost about 60 dirhams. The journey takes about 5-6 hours and offers some spectacular views of the atlas mountains. You may wet yourself on the journey, not only because the bus has no toilets but because the driving is pure scary. i LOVED this bus ride because you see loads of isolated villeages, poor people, market towns. Its amazing . About 3/4 of the way there the bus stops at a highway building which has 'toilets', food stalls and lots of flies and a nasty restaurant. There are chickens hanging up in outbuildings and the flies are everywhere! definately recommended to see the real morocco !
I don't really recommend walking around on your own if you're a female. We got a lot of shouts when we went out and about, so we got taxis instead. They were very cheap - a trip usually worked out to 2 euros (20 dirhams), but if you speak French, then you won't get ripped off as easily as English-speaking tourists possibly would.
You'll recognise the small red-orange Fiat taxis, but they're a bit of a bone-shaker! :)