A rokubox is a one time fee.
It's a small little device, hooks up to your TV, comes with a remote, and has tons of apps that support every website that you would want to watch from your TV, Hulu, Netflix, Amazon Prime, Youtube(not too sure about google video stuff, haven't tried recently). It has a couple hundred channels beyond that, such as MSNBC video and bible stuff too.
A roku is an all in one media streaming device that doesn't require any setup by yourself beyond plugging it in. There are other solutions, such as an Apple TV, but most of those don't have nearly the features of the Roku. If you setup a HTPC in your living room with browser support, it's probably not as necessary to get a Roku, but for an all contained box, Roku's are great.
I'll be buying a second one this year for my second tv.