For 2nd Gen Toyota Tacomas (2005, 2006, 2007, 2008, 2009, 2010 and 2011 models), one of the most popular cold air intakes is the K&N AirCharger 63 Intake. The 63 series uses K&N's latest designs to improve the power and gas mileage of both the 4.0L V6 Tacomas and the 2.7L 4-cylinder models.
Installation of this cold air kit into your Tacoma takes less than 90 minutes usually, and the K&N 63 is backed by a 1 year warranty.
For 1st Gen Tacomas (1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004 years), the K&N FIPK Air Intake is the recommended model. It's available for the 2.4L & 2.7L 4-cylinder Tacomas, as well as the 3.4L V6 model.
More info on the K&N AirCharger.