Due to the alluring combination of robust yields and steadily rising distributions, master limited partnerships (MLPs) have soared to the front of the income investment lexicon over the past several years. MLPs are defined by the fact that they generate at least 90% of their income from commodities, natural resources or real estate holdings, they are entitled to a much more cost-effective tax structure than traditional corporations. This allows investors to enjoy solid payouts and yields while deferring their tax obligations until they liquidate their MLP investment. MLPs also pay no taxes on the income they generate, rather the obligation for taxes is passed onto unitholders, but it is not based on the MLP's net income. These favorable tax factors contribute to investors' love affair with MLPs and it is fair to say the tax benefits of this asset class are widely known by those that can be called "seasoned" MLP investors. While MLPs are obviously quite different than traditionally structured corporations, there is one thing they share in common with regular stocks. Just as the biggest companies tend to garner most of the mainstream financial media's attention, the same can be said of MLPs as the likes of Enterprise Products (NYSE:

), Kinder Morgan (NYSE:

) and a few others are on the receiving end of most of the mainstream attention paid to MLPs. Not surprisingly, that also means there are some MLPs currently flying under investors' radars that are worthy of consideration this year.

Access Midstream Partners operates as a natural gas gathering MLP with operations in Texas, Louisiana, Oklahoma, Kansas, Arkansas, West Virginia, and Pennsylvania. That means the company has exposure to some of the most lucrative North American shale plays such as the Barnett Shale, Haynesville Shale and the Marcellus Shale. Part of the reason that Access Midstream is not yet as well as the Kinder Morgans of the MLP world is that this MLP simply is not an old public company. Its units debuted in July 2010, but investors that were lucky enough to buy and hold at that time have enjoyed returns of over 54 percent along with eight distribution increases. That is to say Access Midstream has doubled its payout in less than three years. Access is

. Perhaps more importantly, Access has seen some

. Remember, insiders sell for multiple reasons, but they only buy for one: Because they think the stock is going higher. Access currently yields 4.9 percent.

Like Access Midstream, Western Gas Partners is not the oldest MLP on the block. It was spun off from Anadarko Petroluem (NYSE:

). Translation: Western Gas provides midstream energy services to Anadarko in West Texas and the Rocky Mountains area, among other regions. Recent analyst action on the stock shows the sell-side is expecting some upside in Western Gas

. Splitting the difference at $55 is still decent upside from current levels. Western Gas Partners yields four percent, which is mild by the standards of many MLP ETFs. However, it is worth noting the payout has grown by 67 percent since late 2008.