If you can turn a screwdriver this is what I'd do:

http://www.newegg.com/Product/Product.aspx?Item=N82E16817182154

I use these myself and I suppose you may find some for more/less but these are very simple to use and dependable @ $20. The satin finish exterior aluminium case also is a good heat exchanger. The use you detailed is similar to mine, I connect to the computer and leave the unit powered off until ready to use then switch on and off again when done. The power switch is a slider located between the two wired connections on one end and easy to find when not looking at it. I mount them on a vertical surface under the desk but it comes with a slip-on stand for desk top too.

The following link is for a hard drive that you put inside the enclosure. It is very simple and the instructions are straight forward. A small phillips screwdriver all that's needed. The connection will work one way or the other  no worries. 

http://www.newegg.com/Product/Product.aspx?Item=N82E16822136292 

I think 80GB @ $23 is a decent size to begin with but you may put a 2TB in this case too, up to you.

enjoy!

* If you want a simple plug in an use model this is capable for your need.

http://www.newegg.com/Product/Product.aspx?Item=N82E16822136606

This a good price though I don't think a good buy because if a problem occurs I prefer to remove the hard drive with my information and get another box.