AAVSO observer, Bob King, wrote a piece in his blog called The Biggest Star in the Sky and How to Observe It. [1]
It's a great introducton to VY Canis Majoris, a hypergiant star approximately 2000 times the size of our Sun.

It's a nice non-technical article with several great images. Check it out! [1]
Links:
[1] http://astrobob.areavoices.com/2012/01/28/the-biggest-star-in-the-sky-and-how-to-see-it/
[2] http://www.aavso.org/forums/variable-stars/long-period-variables-lpvs