TTM is an oft-used acronym -- investor short-hand for "trailing twelve months."
The usefulness of "trailing twelve months" for investment research cannot be overstated. Rather than stick with the hidebound method of only looking at full published years of fiscal results -- 2008, 2009, 2010 -- the "TTM" investment researcher looks at the most recent four quarters of business performance as she ferrets through financial statements looking for The Truth. And The Truth is much more likely to be contained in this four-quarter lookback, than in ignoring quarterly results that have occurred since the closing of the previous fiscal year.
This is all a rather verbose way of saying, "Fools, look at the TTM. When you're doing your investment research, no four quarters are more consequential than the most recent four."