The internal structure of jets produced in pp collisions at the LHC is measured using the ATLAS detector in an inclusive jet sample corresponding to 35pb-1 of pp collisions at sqrt(s) = 7 TeV. Classical jet shape and energy flow measurements are complemented with measurements of new substructure observables with comparisons made to several leading order parton shower Monte Carlo programs. The jet invariant mass and \kt splitting scale are measured for anti-kt jets with a distance parameter of R=1.0 and Cambridge-Aachen jets with R=1.2. Furthermore, a splitting and filtering procedure is applied to the Cambridge-Aachen jets. These tools are then utilized for the first measurements of the filtered jet mass at the LHC in the inclusive jet sample as well the W+1 jet sample, in which a hadronic W mass peak is observed in the jet invariant mass spectrum. A sample of candidate boosted top quark events is also analyzed in detail for the jet substructure properties of hadronic "top-jets" in the final state. Show Partial Abstract