Tripods can help one take better photographs. Many photographs, especially at longer focal lengths, suffer varying amounts from the blur of camera shake. The disadvantages of tripods are that they are bulky and heavy and inconvenient. Some camera bodies and lenses have built-in image stabilization, but they are often expensive.
I spent a few weeks shopping for tripods, and these are the notes I kept.
I had a cheap tripod until my DSLR broke the head so that it could no longer be used. It's worthwhile to buy a better tripod because it can last a long time, and it holds its value. Some photographers point to Thom Hogan's article. His recommendations are still expensive at $600 though.
After reading forum posts, I decided to go with the Bogen 3021BPro for $150 from binoculars.com (after google checkout discount). The 3021 series is recommended as a sturdy though heavy (~5.3 lbs) tripod. The B series are black, and the Pro series costs $10 more and weighs a few more ounces, but it allows a horizontal positioning of the center column, which can be useful for macro photography over a flower, for instance.
I also considered a Bogen 3001BD. The B is again black, the D model costs more than the N models because they have flip levers on the legs instead of twist locks. The 3001 series is lighter than the 3021 series, but they are much shorter: 47" high without a center column, and 57" with the center column extended. The 3021 is 53" and 70" with center column.
Other options: Feisol is a Taiwanese company that makes affordable carbon fiber tripods, and they are mainly sold direct from the manufacturer. The Slik 700DX is a more affordable option, but it's a little less flexible and it only comes in silver.
For a head, I bought a used Bogen 488RC2 ball head for $80. The ball heads are much more flexible because you have one knob to release the ball to move any direction. Also, ball heads are more compact than the pan and scan (3D) models, which have three levers sticking out. The 488 costs a bit more than the 486, but it is sturdier and it has a panning base. The 486 is the cheapest current ball head available from Bogen.