The Wikipedia structure is:
Note the empty bond at far-right.
"Journals on the Web" has:
CH3 added at far-right.
And rxlist.com shows:
There's an extra H going into the page! Is one of these incorrect, or are they all consistent but w/ some implied bonds or something?
There are often shortcuts taken in drawing complicated molecules, particularly if there's not any interesting chemistry going on at those functional groups.
The $\ce{-CH3}$ is implied at the end of the "stick," just like how the carbon atoms aren't explicitly labeled in the benzene ring.
Hydrogens are rarely explicitly drawn for the same reasons, given that you can infer the hybridization by inspection.
See Skeletal formula for more details. Briefly:
Carbon atoms are usually depicted as line ends or vertices with the assumption that all carbons have a valence of 4 and carbon-hydrogen bonds, usually not shown explicitly, are assumed to complete each C valence. A skeletal formula shows the skeletal structure or skeleton of a molecule, which is composed of the skeletal atoms that make up the molecule.
They are all consistent. With line diagrams, all bonds to "nothing" are actually implicit bonds to carbon (this is why the benzene ring and carbon tail can be drawn without $\ce{C}$ in each of your diagrams). In addition, hydrogens are added implicitly until each carbon is saturated. So they are all the same structure.
