Lights, Mirrors, Horns, Helmets
Accessories alone won't make you safe. You also need to know How to Not Get Hit by Cars. Stock up on accessories, sure, but also make sure you learn how to not get hit!
Lights are absolutely essential for night-time riding. Sure, this should be a no-brainer, but for some reason most night time riders seem content to tool around in the dark, almost completely invisible to motorists. Most cyclists who get killed are hit at night, and most don't have lights.
A headlight is actually more important than a tail light. That's because you're much more likely to get hit from the front (car heading towards you making a left turn across your path), or from the side (car pulling out of a driveway or side street and moving right to left across your path). When cars approach you from behind they approach you slower (because you're riding away from them), and if you have reflectors that's usually sufficient to be seen from the rear. From the front and the side it's another story. Get a headlight. Most states require a headlight for night time riding anyway. Make sure to get an LED light, because the batteries last about ten times longer than in a conventional light.
A mirror is more important than you think. Your paranoia will decrease by 75% once you can see what's behind you. You can get a handlebar mirror at bike shops and even many large grocery stores. You can also get a helmet mirror or a sunglasses mirror from a bike shop for about $10. The ones that go on your sunglasses make you look like a Borg, which can be a good or a bad thing depending on your personal style. The newest kind of mirror is a tiny circle on a pivot that glues to the inside of your sunglasses! It sounds crazy, but it works great. Here's a site which reviews various bike mirrors.
Horns. Another extremely handy device is an Air Zound horn. It's LOUD! If a car blasts you, you can blast them right back! The horn mounts to your handlebars, and the air cannister is shaped like a water bottle and fits in your water bottle cage on the frame. You refill it with a standard bike pump, and it's good for about 20 good blasts between refills. We use it when we're biking at night and there's someone ahead of us on the right who's about to pull out of a driveway or parking lot. Never again do we need to worry that they can't see me. The horn can also scare off some (but not all) dogs. It's pricey ($20-30), but worth it.
Helmets. Don't confuse wearing a helmet with bicycle safety. A helmet only makes it safer to crash, but does nothing to make it safer to ride. A helmet might only help once you've already been hit. Your goal is to avoid getting hit in the first place. To that end, you can greatly improve your chances of not getting hit by getting lights, a mirror, and an Air Zound horn, by not riding recklessly, and by being aware of the main ways a car can nail you (pulling out in front of you from your right, making a right-hand turn in front of you, and opening their door in your path). Also remember that a helmet doesn't make you invincible -- helmet-wearing cyclists get killed with depressing frequency. All this aside, it's still a good idea to wear a helmet because it may afford some protection in the event of a crash, but don't think that strapping on a helmet makes you "safe" -- being knowledgable, alert, and well-equipped will go a lot farther toward protecting your life than simply strapping on a piece of styrofoam. Here's a good page about helmet facts & myths from the Ontario Coalition for Better Cycling.
Make sure you know how to adjust your helmet to fit properly. If you wear it wrong it'll come off in a crash, erasing any safety benefit you might have gained. Thrift stores like Goodwill have helmets for as little as $2. Used helmets may be less effective if they've been dropped or impacted in a collision, but if you're pressed for funds, a cheap helmet beats no helmet. A good helmet at a bike shop starts out at around $30, but the folks at a bike shop can also show you how to make sure it fits properly, which is important. Wearing a poorly-fitting helmet is often like wearing no helmet at all.
Locks. In most cases you should secure you bike with either a metal U-lock or a thick cable loop, like the Specialized Hardlock Rapper. Standard cable locks are NOT acceptable in urban areas, unless (1) Your bike is cheap, (2) you're not parking it in public overnight, and (3) you're not parking it at a college campus. Even then, you might still lose your bike with a cable lock. According to Sgt. William Van Horn of the University of Texas Police Department, 95% of the bikes reported stolen to UT police were locked with cables. (From Austin American-Statesman, 11-22-99)
Sure, U-locks are not 100% thief-proof, and the cheaper U-locks are easier to break than the expensive ones, but a cheap U-lock beats a thin cable any day. Home Depot has entry-level Kryptonite locks for $14.95, and Bike Nashbar Online has U-locks for $8.90 + $4.75 shipping. Quality U-locks at bike stores are generally $30 and up.
Baskets are incredibly useful and allow you to use your bike as a replacement to a car. With large baskets and good rope or cord, you can haul anything except large appliances. We routinely carry four 1-gallon jugs of water (two jugs in each side, 30 lbs. total) home from the store. We can fit up to $40 of groceries in our baskets -- or a briefcase in one side and a guitar in the other (which we did when going to the airport to catch a plane to El Paso). We even tied a four-foot stone pedestal to our baskets to haul it home, and hauled a two-drawer filing cabinet by tying it on securely.
Most bike shops will not stock the largest baskets available -- they'll have to order them for you if you want the big ones like ours. The added weight is negligible -- the stuff we haul in our baskets weighs a hell of a lot more than the baskets themselves! We've biked around Austin almost every day for ten years with the largest baskets available.
Pants Clip. A metal pants clip for your right ankle area can keep your pants from hitting your chain and getting greasy. You can also use rubber bands, of course.
Fenders keep rain and mud from splattering on you from your tires. A bike shop can add them to most bikes.
Flat-Free Tires. We have coverage about flat-free tires on a separate page.