I love 5.11 pants, except for thier waist, they advertise it as a "comfort waist" with the elastic liner, it's not that comfortable, I wish they would do away with that feature.
Thier BDU's are awesome though, there are pockets inside the cargo pockets to keep stuff from bouncing around too. And these have a much more comfortable elastic waist adjustment.
Arborwear is great stuff too, 100% nylon but they don't feel like it, made in the USA:
http://arborwear.com/details.cfm/prodid/10
TAD gears stuff looks good if you can stomach the price, all the rest of thier gear is top notch, however these will only work if you're a short guy:
http://www.tadgear.com/x-treme%20gear/apparel%20main/force_10.htm
that bothers me because I'd love to have a pair of these but they would never fit me, oh well.
Another option I'm looking at are these:
http://www.dropzonetactical.com/clothing/opsset.html
they have 100% nylon, 50/50 nylon cotton, and 52/48 cotton nylon versions
Filson, uber expensive, probablu uber nice:
http://www.filson.com/product/index.jsp?productId=2092293&cp=2069836.2069840.2075076&page=2&doVSearch=no&pageBucket=0&parentPage=family
these are what I wear:
http://www.511tactical.com/browse/Home/Law-Enforcement/Pants/Tactical-Pants/Taclite-Pro-Pants/D/30100/P/1:100:10000:10100:10101/I/74273
and they're great, 65/35 polly/polly cotton mix, lots 'o pockets, gusseted crotch, double seat and knees, wide belt loops to support alot of wieght, and they make them in man sizes! The knees can accept an internal knee pad, very nice pants overall, so far these are the best option I have found for outdoor pants, I hope I helped someone with this post