D uring times when sustained growth of the U. S. economy appears less than certain, e-commerce ETF and e-commerce fund represent two investments that can deliver solid gains from virtually assured growth of the e-commerce industry.

According to Forrester Research, the U. S. e-commerce industry grew 12.6% in 2010 to $176 billion. The market research firm expects the U. S. e-commerce industry to expand by 60% to $279 billion in 2015.

E-commerce Stocks in Retailing & Entertainment

The number of consumers shopping online is increasing as unemployment levels rise, transportation costs soar, and e-retailers provide incentives like free shipping. Smartphones and tablet computers are the most popular items sold online.

Improvement in download speed and reliability is prompting increasing number of consumers to fulfill their entertainment wants online. Purchases or renting of books, music, video, and games are rapidly moving online.

Amazon.com (AMZN) and eBay (EBAY) are dominant online retailers while Netflix (NFLX) has entrenched itself in online movie delivery. Groupon, which is reshaping e-commerce with short-life discount coupons from local stores, has filed an S-1 with the intent of becoming public.

E-commerce Stocks in Advertising

Online ad spending in the U. S. is poised for strong growth as more people spend more time online. eMarketer forecasts ad spending to increase by over 20% to $31 billion in 2011 as new formats like video and new channels like mobile and social media gain adoption.

While search accounts for a major share today, growing popularity of video and brand-building ads is helping display ad spending to power ahead. Spending on display ads is expected to exceed spending on search ads by 2015.

Investment opportunities here include shares of search leaders Google (GOOG), Yahoo! (YHOO), and Microsoft (MSFT). Smaller service providers like ValueClick (VCLK) represent potential takeover plays. Facebook and LinkedIn (LNKD) are capitalizing on the growing popularity of social media.

E-commerce Stocks in Travel

eMarketer estimates online sales of leisure and unmanaged business travel in the U. S. will increase 8.5% this year on higher airfares, hotel rates, and ancillary fees. Nearly 11.8 million new users are forecasted to make their travel booking through mobile devices.

Overseas, online airline ticket purchases and hotel reservations are increasing at a breakneck pace. Growth is notably strong in China, South Korea, Brazil, Russia and India from both increasing domestic and international travel.

Online travel and related services companies like Expedia (EXPE), priceline.com (PCLN), and to a lesser extent Orbitz Worldwide (OWW) stand to benefit from the increase in online bookings.