There are a lot of options you could go for. As far as 3 day routines go you can't beat a good old Push/Pull/Legs routine. The idea is that you combine all pushing exercises on one day (ie. exercises that use your chest, triceps and delts) and all pulling exercise on one day (exercises that use your back and your biceps). The purpose of this is to make sure you're allowing your biceps and triceps to get enough recovery seeing as they are being used in the big back and chest/shoulder compound exercises (respectively) already.
A typical routine would look like this:
Push Bench Press
Incline Bench Press
Shoulder/Overhead Press/Military Press
Dips
Pull Deadlift
Rows
Chin Ups/Pull Ups/Pull Downs
Curls
Legs Squat
Leg Extensions
Leg Curls
Calf Raises
I'm a relative newbie myself (training since Feb) and I've been really really happy with my results using this routine, so there's no reason you shouldn't either!
Alternatively you could try a 3 day full body routine. Or you could try one of the tried and tested 5x5 routines such as
Mark Rippetoe's Starting Strength routine or
Frankie NY's Mass Routine (which is pretty much based on the push/pull routine).
If you're trying to gain muscle mass the most important thing is that you're eating enough (good fats, low GI carbs and LOTS of protein), so if you're unsure about your diet then head over to the Diet section of the forum and they'll help you out!
Good luck
<message edited by CitizenKane on 31 October 2009 23:19>