If you're looking for Mac dictation software then you may be disappointed with the limited number of options available.
Express Dictate is a simple but very effective dictation tool for Macs that allows you to record and send voice notes in seconds. Express Dictate works exactly like a dictaphone. You can add brief labels and notes to dictations so that you know what they're about and you can even import recordings made on a portable dictaphone by virtue of the Express Dictate 'Dock' feature.
Express Dictate records in WAV, MP3, or DCT formats and you can perform basic editing of your recordings without damaging the original, which is always archived. Another interesting feature is that, if you purchase the complete app, you also get a foot pedal which will assist secretaries in taking down dictations. Perhaps most usefully, there's a an inbuilt sender that allows you to instantly send recordings by email or FTP. This is ideal for those who want to send something more personal than just an email to friends and family.
Overall, Express Dictate is an excellent tool. The price tag may put some people off but if you're serious about dictation, you can't go far wrong with it.