From the Users Guide:
You can sync Notes in either of the following ways:
In iTunes, use the iPod touch settings panes to sync with Mail on a Mac or with
Microsoft Outlook 2003, 2007, or 2010 on a PC when you connect iPod touch to your
computer. See “iPod touch Settings Panes in iTunes” on page 46.
In Settings, turn on Notes in your MobileMe, Google, Yahoo!, AOL, or other IMAP
account to sync your notes over the air (iPod touch 3rd generation or later) with
those accounts. See “Adding Mail, Contacts, and Calendar Accounts” on page 20.