With all the uproar in the past couple of weeks about a viscous malware hitting Macs you may have interest in something to help you look for it on your computer. ClamXav is a free virus scanner for Mac OS X. It uses the very popular ClamAV open source antivirus engine as a back end and has the ability to detect both Windows and Mac threats. You can download it at: http://www.clamxav.com/
Its very easy to use. The first time you open it you will have to allow it to update itself to make sure it is current on all the things it should search for. Then you tell it to start the scan. If it finds any problem items you can delete them. Use it daily or periodically, but always let it update before you start the scan process.