Captain Morgan White Rum is the brand's only un-spiced, un-flavored white rum. While it's definitely a mixing rum (i.e., it's not all that great straight or on the rocks), it's generally regarded as being a pretty decent product for the price. Distilled five times, it's quite a bit smoother and, ironically, superior to its primary competitor Bacardi Superior. It's probably not going to win too many medals, but you could do a whole lot worse.
Captain Morgan Rum was first produced in 1944 by the Seagram Company. The brand is named after the real-life Sir Henry Morgan, a famous 17th-century Welsh privateer of the Caribbean. It is best known for Captain Morgan Spiced Rum, but also produces a number of flavored rums and limited-release products.
For more, here's a review of Captain Morgan White Rum.