For most of my tripod photography, I use a Cullmann MB6 ballhead, which retails around $160, is made in Germany, and performs exceptionally well for the price. Unfortunately, the head ships with a QR mechanism (MX445) that is absolute junk. The tiny square plate included with this system does not grip my 60D securely with a standard zoom lens, and I imagine would perform even worse with a full-frame camera. Cullmann also includes a standard "screw platform," but this tends to loosen itself from the ballhead and is difficult to to attach to the camera.
Several manufacturers sell aftermarket Arca-style clamps. Really Right Stuff and Kirk are among the best, but a clamp and plate from either company runs well over $100 and the Kirk units are incompatible with anti-rotation bosses used by several ballhead mfg.'s including Cullmann. An inexpensive alternative is the Desmond arca-style clamp, which goes for about $30 on Amazon or B&H. I decided to give this clamp a try based on positive Amazon feedback (admittedly a risky proposition).
Having used the product for an "entire" two days, I have to say I'm impressed so far. The clamp seems solidly made and holds the $12 Desmond plate securely. The plate itself has a d-ring for easy camera mounting, rubber pads to grip the DSLR body, and "safety screws." The clamp also includes a fairly useless removable bubble level, which I promptly removed. Time will tell regarding this clamp's durability, but it does seem well-made and is much more secure than proprietary mounts such as Cullmann's and Manfrotto's 200-PL.