Good green-manure seed mixes

Ever since watching that BBC special on Permaculture, wherein one farmer described how her father figured out the perfect pasture forage grass seed mix with something like 20 different species (what I wouldn't give to see that mix breakdown!), I suddenly thought to myself that the same presumably goes for cover crops and green manure. The more diversity within the seed mix, the more net benefits for the land and the more weed competition. I've looked up a few seed mixes available commercially, but I'd love to hear from you seasoned permies what different mixes you prefer, especially if you use certain species not often found in standard agriculture!

"winter rye, field peas, ryegrass, crimson clover and hairy vetch"

"60% field peas, 25% oats, and 15% hairy vetch"

"crimson clover, mustard, red clover, and ryegrass"

"rye, ryegrass, common vetch, field peas"

My biggest problem with normal green manure seed mixes is that most of the plants are best suited for cooler and wetter climates.

Plants I like for our high desert climate include: barley, chicory, buckwheat, sweet clover (yellow or white), pinto beans, black eye peas. You can buy the beans and peas at the grocery store.

I would put some radishes and/or beets in there for extra organic matter in the soil. Maybe sugar beets.

We planted and grazed a mix of cowpea, vetch, lentil, forage sorghum, crabgrass, and turnips this past summer. Turned out really well, tons of organic matter. We strip grazed 160 cow/calf pairs for a month on 30 acres of it, giving them two slices per day. It would work quite well for a green manure/soil building mix. Even in drought conditions it produced very well.

If you plant in the fall, cereal rye is really good. Wheat and triticale are pretty good as well when planted in the fall. I prefer a mix of legumes, grasses, and brassicas.

My winter mix this season is daikon, blue lupin, mustard as well as extra seed that I've saved including upland cress, Swiss chard and red Russian kale. It doesn't freeze here and I've found rye a bit of a pain if it's not winter-killed. I need to find a wimpier cereal. Fava beans are fantastic, but they're very tall and really only work on their own. Food, nitrogen, biomass and carbon

I also like buckwheat because it is so fast growing - most parts of the US could grow 3-4 crops per year - even Alaska.
You can mow 30 days after sowing! If you find any bare spots in your mixture, you can throw a handful of buckwheat there, and have green growth there in a few days.

For a good, free read on cover crops, try this:
http://www.sare.org/Learning-Center/Books/Managing-Cover-Crops-Profitably-3rd-Edition
At the bottom of the page there are links to either download a PDF, or view a HTML version. The HTML version is easier to read online, as it contains hyper-links to jump around from chapter to chapter, appendixes, etc.
There is also a link to buy the printed version - worth every penny of the $19 if you want a hard copy.