I run Carhartt pants every day at work so here's a short review of the two types of loose ones in my rotation.
http://www.carhartt.com/products/carhartt-pants/Washed-Twill-Dungaree---Relaxed-Fit-B324
The B324 is a nice mix between relaxed and loose fit and is the most durable pant I have ever owned. The photo on the Carhartt website is not accurate to actual fit so I embedded the second image that is closer to reality. These are kind of the perfect medium fit that can look good with cup or vulc soled shoes and whatever top you want to do. The olive is my favorite color followed by the khaki. The black fades quite a bit. Even working construction these will last me 3-4 years a pair.
http://www.carhartt.com/products/carhartt-pants/Carhartt-Force-Tappen-Cargo-Pant-101148The Force Cargo is a great hot weather pant and something that looks different from everyone else's BDU ripoffs. The seams are kind of busy but not as pronounced as in the picture. If you skate in the summer they are the coolest and quickest drying pants I have ever found. They are lifesavers when working on roofs or concrete pads in hot weather. The fit is pretty baggy but not ridiculous and the pockets and tabs stay intact instead of flopping out after three washes.
A couple of fit tips if you're ordering instead of buying in person. I always add +1 inch to waist size on Carhartt compared to any other pant and since they need to fit over my boots I add +2 inches to inseam. They will high water on you over time if you do not. Cricketclub is right about their shirt sizing being all over the place. I usually order a size down from normal and it's still a little big. In person buying is best and Boot Barn, Sportsmans Warehouse, Bass Pro, etc. will almost always have them in stock and sometimes run really good sales.
Carhartt does cost more than some other brands but in my experience they last much longer and when I move it from the "work" to "skate" stack they still look good.