Long TIPS/short treasuries is a fairly "clean" way, just remember in the short-run your returns will be from changes in inflation expectations, rather inflation itself. But it's a pretty good proxy. If inflation rises to 5-6%, treasuries will get hammered whereas TIPS will maintain their returns.
All the other methods recommended have massive exposure to individual markets. At least use a general commodity ETF e.g. the Jim Rogers one. Don't buy one commodity and expect it to nicely track inflation.