Bike Tools

There are a few tools that make your life so much better (ok not really, but at least you won't have to go to a shop to fill your tires with air). The essential ones are:
  - Bike Pump - A small electric one is a decadent luxury, otherwise a floor pump with a psi gauge is good enough.
 -  Tire Levers - I used to use screwdrivers and somehow never popped a tube. Then after I got the levers I popped a tube with a screwdriver (don't use screwdrivers).
 - Chain Lube - A $3 quart of motor oil will last years. Commercial chain lube keeps your chain cleaner though.
 - 14 or 15mm wrench - For your axle nuts (if your bike isn't quick release). An adjustable works fine too if you know how to use it (make the jaws grip as tight as possible, and re-tighten after every turn).

There are more specialized tools that are necessary for advanced repairs. If you have a newer bike you'll probably never need these, but an older bike might have wobbly wheels, or loose bearings. These are easily fixed with the right tools. Good special tools include:
 - Spoke Wrenches - These are almost a must have. I like the individual Park Tool versions. Use these to straighten wheels by tightening the spokes opposite of the wobble, You can also loosen the spokes on the same side of the wobble if the other side is tight. You can also build wheels from scratch with these.
 - Cone Wrenches - These are necessary for repacking wheel bearings and properly adjusting them afterward. A pair of 13/14/15/16mm combination ones are sufficient for 99% of hubs.
 - Cassette/Freewheel Remover - These are specific to your bike. All Shimano and Sram cassettes use the same cassette tool. Freewheels (the older gear cluster style) use a vast number of different tools. You'll need to remove the gear cluster to replace broken drive-side spokes, or repack the rear wheel bearings.
 - Chain Whip - Used to hold a cassette in place for removal, or to remove a fixed gear cog. You can make one yourself with a 3/16ths" thick steel bar and a length of old chain.
 - Crank Puller - Used to remove square taper or splined cranks from the bottom bracket spindle.
 - Bottom Bracket Tools - There is a large splined socket used to install or remove a cartridge bottom bracket. Adjustable bottom brackets typically need a large adjustable wrench and a lockring tool. Outboard bearing bottom bracket cups use a very large wrench with round "toothed" jaws.
 - Headset wrench - Not entirely necessary for threaded headset adjustment, but makes things a lot easier. I typically use a vice grip with a towel between the jaws and the cup to hold it in place since I don't even have one.
 - Allen wrenches - Typically you will need 4, 5, and 6mm versions on newer bike parts. An 8mm Allen socket is useful for certain crank bolts.
 - Chain Tool - This is necessary for installing or removing most chains. Even on chains with a master link, you will still need this tool to cut it down to the right size.
 - Big Adjustable Wrench - This is a must-have if you intend to remove bottom brackets or headsets. A 12" or larger should suffice.

That about covers the tools needed for most bike work. Certain repairs are best left to a shop, such as headset cup installation or derailleur hanger alignment, since the tools needed are very expensive. I will post in-depth tutorials for more advanced repairs later on.