My Suggestion (October 2012)
The first thing you need is a good carry strap. I have recently swtiched to the BlackRapid RS-7 which is great for walking/hiking. I rarely use a tripod and if I need some extra support then I use my BushHawk shoulder mount.
For those with heavy lenses that use a tripod 100% of the time then I would go with the Gitzo that would last a lifetime. I would also add a Gimbal head to that tripod. Another popular combo is using a shoulder mount on top of a monopod. But this requires customizations and it is up to the user to perfect this setup since I have not found any such reseller.
You can accomplish maximum stability for your spotting scope, or camera setup by using a heavy, wooden tripod with spiked feet, without a center column, and with a heavy head such as a ball head. But note that you might end up
leaving the heavy tripod at home if you plan to move around a lot.
Gitzo have long been the choice of the professionals. They have a good reputation hence the steep prices. Gitzo 3530 LS Carbon Fiber tripod ($725) is very popular with photographers. A short Gitzo tripod guide: Tripod for...
Manfrotto, or Bogen as they are called in the USA are very sturdy and considerably cheaper than Gitzo. They mainly use protruding, flip lever leg locks. After extensive use these locks might fail. You should always carry with you a wrench to tighten the nuts of the bolted locks, especially if you are going on a longer trip to a sandy destination.
Benro is yet another budget tripod manufacturer. They are price worthy and of good quality. Benro C-257 ($380) was my choice and alternative to Gitzo 3530 LS.
But note that there are many more good and cheaper manufacturers out there. Try one out for yourself. Remember that spiked feet are great, but you would love the easy switch to rubber feet as well. You should also not select a tripod that is very heavy since you might just opt out, and not bring it along.
Monopods are very useful in good light. But in most circumstances a tripod is to be preferred. Manfrotto/Bogen 681B ($50) is a large sized aluminum monopod that is extremely sturdy. But I prefer Velbon CF-7 ($130) which is a slightly smaller Carbon Fiber pod with an ingenious antirotation twist leg lock, and a useful shoulder carrying strap. Both monopods are insulated at the top of the monopod, and the leg locks only need one hand to resize the monopod.
Skimmer Ground Pod
When getting low on muddy and sandy soil then a tripod can be awkward to move about. Naturescapes Skimmer Ground Pod II($100) is the best product for this type of terrain.
This support is very useful for eliminating camera shake, and blurry pictures. The shoulder mount by BushHawk have an electronic remote shutter release that is coupled to a button on the mounts pistol grip. This greatly reduce the camera shake otherwise induced by pressing the on-camera shutter release button with your finger. You can also use a quick release plate to quickly mount the bottom of the shoulder mount to a monopod. Shoulder mounts are underrepresented in bird photography, but unjustifiably so.
I have since March 2011 used the shoulder strap BlackRapid RS-7. It has made it much easier walking around with the lens, not worrying about it sliding off the shoulder.
Fluid video heads
Manfrotto has made very good versions. It usually has a flat base fluid video head with a very smooth, adjustable movement on both axis. A Quick Release platform which is forward/backward adjustable to balance the weight better. Make sure you don't skimp on the head since the cheaper models (e.g., "mini" versions) are often shaky, or they will get hard to move when used in cold temperatures. For heavy lenses you should probably look at a large head like Manfrotto 501 which can take a payload of 6 Kg, but weighs in at 1.6 Kg. Note that photographers with large lenses usually go for a Gimbal head instead.
The latest standard for supporting super telephoto lenses on tripods,
replacing the video fluid head, is the so called Gimbal Heads. The most famous brand is the Wimberley heads ($600). They enable amazing maneuverability for huge lenses, and have been
recommended by the best. The closest competitor and best price are Jobu Design: Black Widow Jr.3 Gimbal Kit($350), and Benro GH-2 ($400)