Variance is it's own little animal with a lot of fuzzy fur and wrinkles, so understanding how trade relative value there is a bit tricky. Now, for first order approximation, you can download the history of VIX, rescale it for the business day count and here you go, you got a rolling history of 1 month variance from the beginning of times. As a retail trader, however, you exposure to var swaps is a bit limited (unless you are running a fairly large book) and you are better off looking into relative value trading of VIX futures and options. There is like a tonn of things you could do there, from simple spreads and flys to fairly complex option strategies. If you add VXX and VXX options (or other VIX etfs), sky is the limit.