Personally, in the summer I go with synthetics a lot more. I simply find cotton bulky, very heavy when it gets wet and really slow to dry. That said, in the winter - cotton can be a great fabric for warmth and generally speaking it is a llittle more pleasant to wear for its softness to the skin.
I absolutely love the columbia UPF50 long-sleeve shirt:
http://www.columbia.com/Product.aspx?top=1&p=4365&cat=15050&viewAll=False
I own six of them. They are extremely light weight, can be rolled and packed to a really small size and keep the UV-rays of my skin (I'm pretty sensitive to the sun). They dry really quick. They have pockets in the front perfect for your Cigar and SAK. Finally they look pretty good, even when you bomb into town.
Second most important item is a really good waterproof hat. My best technical hat is a Tilly hat, one of the high-tech nylon ones. It has this great strapping system (around the back of your head and your chin) where it cannot blow off your head no matter what. It keeps you cool in the sun and dry in the rain. Like the shirts it folds down to nothing when not in use. It has a piece of foam incorporated in the top that makes it float when dropped in the water. It also has a little tiny pocket on the inside of the hat which is great for storing a $20 bill, matches and a bit of firestarter. Finally it is has a lifetime guarantee which includes insurance against lost. Worth the $60 US in my books! Its only problem is that it makes me look like a bit of a geek when I'm in town (okay - maybe its not just the hat). My walk'n around town hat is of waxed cotton made by Outback - looks great, is waterproof but is heavy, gets hot in the sun and can't be folded or crushed out of shape.
For pants, I personally think blue-jeans are the worst thing on earth. When they get wet, they get heavy as hell and they stay wet until you get home and put them in the dryer. Oh sure, you can try to dry them by the fire along with those running shoes. We all know how well that works! I far prefer the synthetic nylons for hiking which have come a long way in terms of softness, fit and styling. I like to pack at least one pair of heavier pants, synthetic or cotton, and a few pairs of the light nylon ones with at least one having the zip-off legs. I prefer cargo-type pants with different pocket options. One thing that is often a problem with synthetic pants is for some reason they often make the belt loops pretty small. Make sure you look at the belt loops before you buy to ensure it will fit your belt and sheath. Also, you should try on any synthetic pants/shorts before buying. As far as I can tell, the size on the tag means almost nothing and nylon won't stretch or change shape like cotton.
Raingear - I've made the switch to goretex jacket and pants to serve both as raingear and for warmth. I've even now invested in two sets of goretex. A smaller packable, non-gortex knockoff, for the summer and a heavier gortex jacket/pants for spring/fall/winter.
I agree with the posting above that good socks are really worth while. I like Marino wool, sometimes referred to as smart-wool (or maybe the later is a brand). Don't both bringing the white tube socks on a camping trip.
