  We present transit photometry of three exoplanets, TrES-4b, HAT-P-3b, and
WASP-12b, allowing for refined estimates of the systems' parameters. TrES-4b
and WASP-12b were confirmed to be "bloated" planets, with radii of 1.706 +/-
0.056 R_Jup and 1.736 +/- 0.092 R_Jup, respectively. These planets are too
large to be explained with standard models of gas giant planets. In contrast,
HAT-P-3b has a radius of 0.827 +/- 0.055 R_Jup, smaller than a pure
hydrogen-helium planet and indicative of a highly metal-enriched composition.
Analyses of the transit timings revealed no significant departures from strict
periodicity. For TrES-4, our relatively recent observations allow for
improvement in the orbital ephemerides, which is useful for planning future
observations.
