Re: gaining muscle mass for tall, skinny guys (I used to be 155lb at 6'2")... If you want to bulk up I would seriously suggest lifting weights. Focus on major muscle groups and forget about bodybuilding and isolating muscles. Squat, deadlift, bench press, military press, bent-over rows, dips, pullups w/weighted backpack. Great stuff for building muscle.

There are many good routines out there. Personally I prefer something based on the push/pull principle where you follow each exercise by working the antagonist muscle groups. Most of all, squat! For starters, something very basic in the range of 3 sets, 8-12 reps might work so that you get used to proper technique. A little later, 5-8 reps could be better for developing real strength without useless bulk. If you can handle the 20-rep squat routine it will build muscle faster than anything else I've ever seen.

A guy with fast metabolism doing this kind of training about 3x per week can realistically expect very good gains (maybe 6lb per month). But you'd need to stay away from long distance jogging for a while because it kills muscle mass! Substitute with intervals, fartlek or other anaerobic training if you want to work on endurance though no more than 1-2x per week if you really want to focus on bulking up.

Also, eat well 5x per day, lots of protein and consider supplementing with a weight gainer. You will need it if you're a real "hard gainer". There are a lot of myths about supplements and many don't work at all but a weight gainer might be worth trying. If you skip meals often you could also get those meal replacement shakes. Again, very handy and great for faster recovery after weights.