A newbie question that I've been failing to get round to asking for a while. In my defence, I'm more inclined towards the software and soldering iron end of the engineering spectrum, and only pretend to know what I'm doing with a spanner.
So yeah: grease. I understand that it tends to be used for one of three main functions: To lubricate moving parts so they run smoothly with less wear; to protect things from corrosion; and to encourage parts to fit together more consistently and/or eventually come apart with lesser degrees of Persuasion.
Supplemental to that, I'm aware that in comes in all sorts of flavours, the subtleties of which may or may not be important for a given application. Thermal grease I understand. Copper grease to prevent parts from seizing makes sense (indeed, I've got a tube of it somewhere, which I use as a talisman to ward off stuck pedals and freewheels). That high-speed moving parts are going to make specific demands in terms of temperature stability and viscosity makes sense, as does the fact that you don't get such high speed moving parts on pedal cycles. I can imagine gear hubs are quite fussy about viscosity, though. I'm also vaguely aware that some recipes are better for keeping water out of stuff (which *does* seem desirable on a bike), that some may not get on with certain plastics, that lithium is what you need for manic-depressive bearings, and I read on a newsgroup that the there's this stuff called molybdenum disulfide that when applied to your chain will allow you to climb hills like Lance Armstrong.
Up until now, I've been lubricating my mechanical bits (chiefly screw threads, but also the odd headset bearing, suspension part or brake pivot) with a small tub of "bicycle grease"[1] that was cheap on Wiggle when I didn't really know what I was doing. It's almost run out, so I probably ought to invest in something else.
So, what do I need, guys? (Answers of the style "get a litre of this from your local chandler for a fiver and use it for everything except hub gears, and it should last you until you're getting birthday cards from the queen" strongly preferred.)
[1] It's white, and tastes bad.
Copper grease is really an unscrewing paste, which is what Shimano call it. Not a lubricant for moving parts.
Lithium grease (may be white, red, or just a big tub of yellow Castrol LM) is your all-purpose stuff. Fairly waterproof and good for bearings.
Calcium grease (Castrol CL) is the most waterproof. May not lubricate quite as well but good for lake jumping, floods etc.
Polyurea grease is the blue smelly Park stuff. Supposed to be best for bearings.
Weird greases: Sturmey-Archer internal gear hub grease is a very thick brown oil. SRAM internal gear hub grease is like a pale yellow version of Colgate Blue Minty Gel.
And then there's that carbon seatpost stuff, which I think is a plastic-friendly grease with little plastic balls in it for friction.
Roller (or coaster) brakes need to run in grease to stop the metal shoes melting, which would give pretty much zero friction. There are special greases available but they're generally molybdenum sulphide greases; horrid black sticky stuff. My SA coaster hub has Ceratec automotive disc brake grease in the brake end. It's rated for 1000 deg C, intended for the back of car brake pads, and works well.