VeloPress has a new book out for Triathletes that helps them add strength training to their regimen, helping them take their performance to the next level without finding time for more swimming, running and cycling.
The cardiovascular benefits of strength training, especially when done in rapid succession (ie. circuit training) are proven, and it’s definitely a way to improve your strength to weight ratio.  I can’t speak for dedicated triathletes, but I know cycling alone doesn’t do a whole lot to train the core stabilizing muscles, even though their used heavily.  So if you’re looking for an edge as a triathlete, or you just don’t want to look like a skinny roadie, check it out.
VeloPress usually has some internal page views and TOC, but they’re not up for this tome yet.  $22.95 for 224 pages of muscle building advice. ($14.93 on Amazon)