I accidently trashed a file!!!

Did you empty the trash? If so you can use time capsule to get the files back.

 

Time Machine and even if you emptied the trash Time Machine should be able to help you recover it. If it is real important and you didn't do a TM backup then you could go to a data recovery place unless you did a secure empty of the trash.

 

IF you've already had it set up.

 

If you have already emptied the Trash and the file is important to you, get Data Rescue 3, as it scans your HDD for deleted files and can recover them, if they have not been overwritten yet. So it is best to leave the writing to your HDD to a bare minimum, meaning not copying big or small files to your HDD, as that might overwrite the old file.

http://www.apple.com/timecapsule/