You might need audio files in different formats to use as ringtones or to transfer to mobile devices for playback, but not all devices support all formats. Switchr is a nice online service which allows you to convert audio files from one format to another. In just a few clicks, you can convert any audio file on your computer into a different audio file type, including iPhone ringtones. Using Switchr.net, you can convert audio files into WAV, MP3, AAC, AIF, AU, FLAC, M4A, OGG, WMA, and M4R formats.
As of now, you can upload files upto 100MB is size. Once selected, you can specify the format to convert to. In case you want a part of the song to the converted, you can select the time and end time for the file from the advanced settings.