What is the cheapest way to get from Eindhoven to Amsterdam?
I'm currently working in our Eindhoven office and can see the runway from here ;)
Hitchhiking is unlikely to work; there's no decent location to get picked up near the airport. The A2 highway is close, yes, but there's no parking lot or something similar. Furthermore, you're not allowed to walk on the highway itself. You'd have to post on the on-ramp, but there's no room to stop there.
The train would be easy, and there are 7 buses per hour to the station. Pick the 401 (22 minutes; it uses a reserved buslane so no traffic jams); the 103 takes a horrible detour. Costs 3 euros one way, and you'll need coins for that.
There are actually 4 trains per hour to Amsterdam; two of them go to Central Station and the other 2 go to Amsterdam Airport (south of the city). Depending on where you're going, either route is an option. All trains stop in Utrecht, where you can transfer.
What about the shuttle service? About 20E according to the website, so costs like the train. Is it worth it?
AirExpressBus? I've never seen one of their buses (and they'd have to pass my office to get to Amsterdam). It seems they only run 4 buses a day instead of 4 per hour. And I don't believe a word of that claimed 1:30 travel time either. The A2 has been improved near Amsterdam, but the southern part is still a work in progress.