AST has been a real good site for me.
http://www.ast-ss.com/
As far as gaining lean muscle mass and keeping body fat down it is very possible. You won't stay ripped all time, but it won't take much at all to get the six-pack after your gains are made. Of your calorie intake, try to take in 53% protein, 37% carbs and 10% fat. Find your
Basal Metabolic rate, this will tell you about how many calories you burn a day if you don't do any activites (walking, chewing, training, ETC.). Monitor your weight and body fat % weekly, make adjustments to you calorie intake accordingly.
Try to keep your cardio and resistance training about 8 hours from each other. For cardio do
high intensity training for 16 minutes in intervals. This will burn more fat more effectivley than running for 45 minutes.
Here is a great link that explains this.
http://www.ast-ss.com/articles/article.asp?AID=97