What is a good travel site offering tour packages to central and south America?

I had a link to a travel site catering to students, but have since lost it. It seemed like the tours cost almost 1/2 as the others I’m pulling up from Google. I just remember it had a simple gray background.

What is the cheapest way to travel to Panama Central America by bus or train from San Antonio Texas?

I would like to travel to Panama sometime this year. I was wondering how much it would be to travel from San Antonio, Texas to Panama Central America by bus or train? Has anyone ever made this trip? I googled it but cannot find an answer. Any websites? Tips and info? Thanks!