It may pay to look at less-often-considered options when assembling a long-term dividend portfolio of exchange-traded funds.

Investment management firm Vanguard offers a variety of exchange-traded funds (ETFs) that allow investors to target a specific theme or sector at a low cost. With just 0.04% expense ratios, meaning $0.

If you're looking for the relative safety of an S&P 500 ETF with a bit more punch, the Vanguard S&P 500 Growth ETF ( VOOG -0.35%) could be a fantastic choice. This ETF also follows the S&P 500, but it only includes 209 stocks from the index that have the most potential for growth.