Cover Retriever is a free software for Windows that makes it easy to add album cover art to mp3 and flac audio files on the computer.
Album cover finder
The search is based on data obtained from the tags of file and processing through Google search engine. The drill is as easy as can be: you just have to select the folder that contains your audio files and let this app take care of the rest. You'll have your covers in just seconds.
The tags search allows you to fill out tags audio file and find appropriate cover. The tags can be easily saved into file by clicking one button. The search is based on Last.fm service to get the best results.