Par-N-Rar is a graphical utility which accepts a directory as input and will repair/verify any PAR/PAR2/SFV/MD5 files in that directory. Once it verifies a set of files, it will attempt to unRAR them. Once it finishes unRARing a RAR archive, it will (optionally) remove the original PAR/RAR files.
Par-N-Rar is open source and is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
If you have any bugs or feature suggestions, drop me a line.