The Manfrotto 055 series is relatively large and reasonably heavily-constructed, of either carbon fiber or aluminum, and with or without the ability to tilt the column. Manfrotto has at least one larger, heavier-duty tripod, and lighter-duty ones as well, in their outdoor-suited line-up, but I have the 055 series, in both carbon and aluminum.
Gitzo is a more-expensive brand, but I bought a discontinued aluminum model at a considerable discount, that seems beefier than the aluminum Manfrotto 055. It awaits a head, so I have rarely used it.
The other part of the equation is the tripod head. I have used Manfrotto 222 heads, with 40D, 7D, and 5D bodies, and lenses as large as the 100mm 2.8L Macro IS and 135L are steady enough. The 222 head is usually OK with my 400mm 5.6L, with the just-mentioned camera bodies, but struggles with my longer, heavier 400mm 5.6L lens on a 1D-series body. If my budget can stand the strain, I hope to add a Wimberly gimbal-type head, for use with my long lens, soon.
Ming Thein blogged about tripods and heads a few months ago. I liked his article, particularly concerning the heads. He uses quite heavy Zeiss Otus lenses on Nikon D800 or D810 bodies, and Pentax 645 system, so anything stout enough for his perfectionist shooting should be OK for a 7D with equivalent-weight lenses. I do not know if, or when, I can justify an Otus lens, but I do have my sights set on a Zeiss 135mm APO lens, and the EF 11-24L, neither of which are light-weight, themselves.
