If you happen to send emails to yourself containing information you want to store for later use than MailNote is just what you need. Select MailNote icon in the menu bar, type or paste text, press Send button and that's it, your information is stored in your mail account. If you prefer keyboard shortcuts to mouse opertations, they are ready to use and fully configurable.
Mia for Gmail (was Notifier Pro for Gmail) is a desktop Gmail client which sits politely in your menu bar.