The Unofficial Sibelius Wiki - your source for tips and tricks to the worlds very best music notation software!
06/09/2010 - SIBELIUS 6.2 - WIKI software updated - Announcements

Export to MP3 or any other format

Sibelius can only output to a wav/aiff file.
To create MP3 files, open the wav (win)/aiff (mac) file created by Sibelius in a downloadable program like Reaper or Audacity (both Windows and Mac OS) and use the export/render to MP3 feature.
You can of course export to other formats, too, that depends on the software you are using.

Another solution is to use iTunes:
Import the wav/aiff into iTunes and convert it to the format you want to have. iTunes allows you to add tags easily and is great when you want to give files to clients that play good on any iPod because iTunes inserts necessary information (gapless playback, remember play position etc…) in the tags.
More about using iTunes to organise your music you can find at itunes_for_sibelius_users.