iLounge provides an extensive roundup of all of the iPhone voice recorders presently available in the App store. These apps are, of course, only compatible with the iPhone and not the iPod touch due to a lack of built-in microphone for the iPod touch. A summary of their ratings are provided here (prices link to App Store):
• Voice Notes (Free, C-) - no-frills. easy to accidently delete recording. no export.
• VoiceRecord ($0.99, B-) - slightly more polished. no pause, no export
• SpeakEasy Voice Recorder ($1.99, B+) - polished. level meter, adjust quality. no export
• Audio Recorder ($2.99, B) - email recordings out of iPhone.
• QuickVoice Recorder ($1.99, B-) - transfer recordings out to Mac or PC. pause/resume.
• Recordifier ($4.99, C) - no pause/resume. no export.
• Recorder ($0.99, B-) - basic recorder. email recordings out of iPhone. no pause.
• Note2Self ($2.99, B+) - designed to email recordings out of iPhone. accelerometer detects usage.
• EccoNote (Free, C-) - poor interface.
• iRecorder ($0.99, B-) - works as advertised. standard UI. no export.
• YouNote (Free, C) - note taking
• Jott (Free, B-) - part of Jott service to record and transcribe to do's.
While iLounge's top picks include SpeakEasy Voice Recorder [App Store] and Note2Self [App Store], it's clear the best choice will depend on your usage. While Note2Self seems well designed for recording personal reminders, it would be less useful for recording lectures. If recording lectures is your goal, it would seem Audio Recorder [App Store] or QuickVoice Recorder [App Store] might be more useful with the ability to get recordings out of your iPhone and onto your Mac.
iLounge provides a much more in-depth look at each application in their review.