The first six weeks of 2010 have been a bit on the tumultuous side, as equity markets that came flying out of the gate have done a complete reversal, heading lower and erasing large chunks of the gains recorded in 2009. While the rocky start has been unnerving for investors anxious over the possibility of a double dip recession, others have found a silver lining in the recent pullback, as some big losses have created attractive entrance points in sectors that now appear to be bargains.

The energy sector sector has been one of the hardest hit in recent weeks, as disappointing earnings reports and concerns over job growth have spooked investors. Unexpected increases in oil inventories and a surprisingly strong dollar have also weighed on the sector in the early part of the year. But after dropping as much as 20% from 2010 highs, some energy ETFs seem to now be offering good value as bargain buys.

It is always useful to look at sector relative changes once in a while, just to spot any phase changes or shifts in leadership.

When I first got into the investment business, a grizzled veteran taught me the basic principles of sector rotation. Early in the cycle, it's the interest sensitives that lead the way. Sector leadership rotates through the equity market spectrum until you get to the asset plays - the inflation hedge stocks at the very end of the cycle.

Oil and related ETFs have experienced huge gains off its last year’s low, and energy companies have pocketed most of the change. However, the oil industry is expanding its options into other energy fields as it anticipates the eventual depletion of oil reserves.

Big western oil companies are trying to sustain reserves by expanding through acquisitions and investment, according to The Economist. For instance, Exxon Mobil (NYSE: XOM) estimated that exploration and capital spending hit $27.1 billion in 2009, or 4% higher than in 2008. The company also expects to continue spending around $25 billion to $30 billion a year over the next five years for the same purpose.