Large items:
       backpack
       smaller summit pack (if desired)
       sleeping bag (down or synthetic, to 30 F at least)
       sleeping pad (closed-cell foam or thermarest style)
       ski poles (if desired; especially if you have bad knees)
       hiking boots (any kind)
       tent (3-season is OK; with rainfly)
 
Items to share with your tent-partner or friends:
       backpacking stove
       fuel
       matches/lighter
       cooking pot (aluminum is better than steel or titanium)
       appropriate cooking utensils (e.g. spatula)
       food for dinner and breakfast
 
Clothing:
       long underwear, top and bottom (light-weight)
       socks (e.g. polypro liner and wool outer-sock)
       pants (nylon quick-drying zip-off pants are very popular)
       wind-pants (if desired), either nylon or Gore-Tex style
       gaiters (if you have them)
       upper layers (e.g. fleece or wool jacket) 
       shell jacket (Gore-Tex style is nice, but not essential; nylon will do)
       down jacket (if you have it; very nice to have in camp)
       hat (wool or fleece)
       gloves/mittens (I bring several pairs)
       balaclava/scarf/neck-gaiter (if its really windy or cold)
       sun-hat (for approach)
 
Personal items:
       utensils and eating gear: spoon, bowl, mug, sharp knife
       food for yourself: lunch, snacks
       water bottles (2 quarts minimum, 4 quarts maximum)
       sunscreen (especially if were walking over snow)
       chapstick with a SPF (especially if were walking over snow)
       watch (for an alarm in the morning)
       flashlight (preferably headlamp)
       extra batteries (unless your batteries are 100% new)
       camera (if desired)
       small first-aid kit (ibuprofen, gauze, band-aids)
       moleskin/athletic-tape or similar (for blisters)
       toilet paper
       WAG bag (these are forest service provided bags that contain a bit of kitty-litter that you defecate into)
       Toiletries (e.g. contact solution, toothbrush/toothpaste)