What about an RSVP Ticker?
Copy and Paste this into your sig, and change the numbers accordingly:
147<img src="http://tinyurl.com/2sdozd">62<img src="http://tinyurl.com/32ch7p">38<img src="http://tinyurl.com/2ts57r">
Congrats on sending the invites! Such a great feeling! And it's even better to check the mail!