I own or have owned all of the following products. I have not been paid by anyone to include these products.
For those who are just starting to ride their bikes to work, school, or to go shopping, I recommend this low-cost and easy-to-install rear bike rack. It won't last forever, but I still recommend it as part of the "learning period" (when you figure out for yourself what you do and don't like).
The best value taillight. It has three red LEDs that alternate and provide extreme brightness. I have two of these.
For u-locks, I only recommend Kryptonite Evolution series (orange) or better (yellow). Kryptonite color codes their lock series. Only buy orange or yellow; never buy OnGuard. I have three of these locks and none has been tampered with.
All three of my current bikes (as of November 2010) have Planet Bike fenders. Two have Cascadia fenders; the remaining has Hardcore fenders. The main difference that I see is the size and quality of the mudflap. I use the 29er fenders on my Yuba Mundo (Cascadia) and the 35mm fenders on my Nishiki Prestige (Hardcore) and Raleigh Rush Hour (Cascadia).
After 45 minutes of non-stop riding, the saddle is no longer comfortable. But it's really hard to find a saddle that is. This one has a cutout to relieve pressure on your perineum. It's a little wider than road or racing saddles. It's foam doesn't lose its shape (I've had mine on the Nishiki Prestige for two years).
An extremely versatile element to carrying cargo on your bike, whether in an overloaded basket, a rear rack, a pannier, or a front rack.
This shirt has two benefits for bicycling: 1. It's compression-wear which gives some benefit to your muscles (or something) and feels very comfortable and makes it easy to move, and 2. It has a warm lining that helps keep your body insulated with its own heat.
I've used this pannier to carry groceries, books, my laptop, clothing, anything. I like it because it's stylish (but also "normal" looking at the same time), stands up on its own, is extremely durable, and has the most universal attachment system: two hooks.
So far my longest trip was 40 miles on this saddle. It molds to your butt like Birkenstock sandals mold to your feet. The springs make the bike ride a little more comfortable and more fun (weird, because you bounce up and down on them). It also looks gorgeous. Comes in 3 colors - I got black.
So far I haven't had a flat with this tire. I've used Continental Gatorskin and Panaracer T-Serv, both of which have had flats (same Chicago streets). The Gatorskin has less tread than both, and wears to a slick surface faster.
I've used this backpack for over three years now; I bought it to replace a messenger bag that led to shoulder and back pain. This backpack is designed with a mesh and shell system that keeps the weight directly off your back so you can stay cool. I'd say this makes it about 15% more comfortable than a traditional backpack - don't buy it just for this reason. Buy it becomes the shoulder straps are comfortable, and that it comes with its own rain cover. It also has a helmet holder, but I use that to hold clothing, shoes, or a frozen pizza (because that doesn't fit inside). The "smallish" size of this backpack prevents you from overloading it. I use it for everyday use, and I also carried books in it for school.
I have four pairs of these that I rotate through the week. Them being wool means they don't smell as bad as cotton or polyester socks; they also dry faster and don't make your feet cold when wet.
The most common hex sizes you'll need for any bike on a single tool: 4mm, 5mm, 6mm. The triangle design makes it easy to get a good grip and leverage.
Cheapest patch kit around.
I bike in these. They are waterproof. They are the only shoe I took to Europe, for 18 days.
These are my spring and fall cold weather gloves. I've had the same model for 5 years (when they used to be called Windfront).
Catch all those bad drivers on the road so if you get into a crash with one of them, you have evidence. See example video I've shot.
Planet Bike headlights offer the best value: quick release, water resistant (don't dunk it), easy on/off, and they sip batteries. I've been using them since 2009. Get Lit.
Note: I generally recommend ALL of Planet Bike’s products because they donate 25% of their profits to bicycle advocacy groups and because of their dedication to good customer service. They also have a lifetime warranty on all of their products.