Now that iOS 6 is out, What you don't have it? Go get it!
Mail has come a long way. One of the newest features is Multiple Signatures. For those who deal with email for personal and Work, and have multiple email accounts on their iOS device. This is a great addition to an already great email app.
Check out the options in: Settings > Mail, Contacts, Calendars > Scroll down to the Mail options.
Tap on the Signature Option Choose "Per Account"
Then You'll see listed a title and a text box for each email account you have setup.
This is great for personal/professional separation on your idevice. Especially in this day of BYOD (Bring your own Device) we all want to make sure our personal info doesn't cross over to our business world.