Photoshop is essential to any work environment. Its not just post production and graphic design. Hospitals use it, law firms use it, even police and crime investigators use it as a means of forensics analysis. Being good at Photoshop has now become one extra skill that looks good on your resume just like Excel or word.
Check out this Six revisions post that has rounded up some internet tutorial that will help you fine tune and hone your Photoshop skills.