No simple resend.
If you don't mind them knowing it's a repeat, just go to your Sent folder, select the email and forward it.
If you want a neater solution, then after you open the old email, tap and hold until you see copy, drag the handles until you've selected everything you want, then copy. Open a new email and tap and hold to paste it into the body, address, subject, send.
To get to your Sent folder, tap the button at the top left of the mail list until you see all your inboxes and accounts listed. Select the account, then the Sent folder. Be sure to go back and select your inbox again later if you want to see your incoming mail, though if you only have one account the inbox under the account list will work just as well as the Inbox at the top.
@davidalan99, the Calendar alert will only let you send reminders to yourself at your default email address.