While I disagree with many of RVAIS' links, I figured it might be useful to add some useful links to the topic instead of scattering them round everywhere. I have no intention of starting a debate on this thread, RVAIS, just adding some links.
EXRX - Useful fitness database, particularly the list of muscle groups with links to exercises that work each muscle (second link)
http://exrx.net/
http://exrx.net/Lists/Directory.html
MOTIVATION - There's plenty in the link below. Find out what works for you, and keep a motivation folder on your computer - music, pictures, videos, anything that works. A playlist titled 'Lifting', with tracks that are suited to weightlifting (eg heavy metal songs with breakdowns) will do wonders for you.
http://forum.bodybuilding.com/forumdisplay.php?f=311
STRONGLIFTS - Brilliant strength program (a strength program is one designed to make you strong before you start a more advanced bodybuilding routine, as progress is faster and it will get you to your goal quicker - also accustoms you to weightlifting)
http://stronglifts.com/
STARTING STRENGTH WIKI - Good strength program, great additional resources. Second link is the programs, Practical Programming is probably the best of them.
http://startingstrength.wikia.com/wiki/ ... ength_Wiki
http://startingstrength.wikia.com/wiki/ ... g_Strength
SIMPLYSHREDDED - Useful information resource for research studies, motivational material, and interviews with bodybuilders. Take nutritional and workout advice with a grain of salt.
http://www.simplyshredded.com/
WEIGHT GAIN - If you want to gain weight, here's the key: Eat lots, drink lots of milk. You might think you already do, but if you're not gaining weight, you aren't (or don't need to be gaining weight). Protein shakes are useful directly after a workout and for convenience (eg you can't eat at your job), but diet comes first and foremost.
http://stronglifts.com/how-to-gain-weig ... inny-guys/
http://stronglifts.com/gomad-milk-squat ... in-weight/
WEIGHT LOSS - Keep in mind that most weight loss is mistermed - people really mean 'fat loss'. This can be achieved simply by making better choices on the foods you eat (less sugars and junk food, more lean meat, vegetables, etc) OR cutting calories and intake or both 99% of the time. I'm sure everyone here knows what food is healthy, so a link is unnecessary - cutting calories requires no link either. Address those first. Only in exceptional circumstances will you require something else, in which case a SPAM diet may be useful:
http://en.wikipedia.org/wiki/SPAM_diet
CHAT