Here's another promotion, this time only on Amazon.com.
With any of the phones they sell on their site (Nokia Shorty, Audiovox Vox and Audiovox V7, Kyocera K10) you not only get free shipping and no tax, but also you get a free $20 topup card if you add it to your cart and remember to put in the promo code. Below is an example (I used the Audiovox Vox because it's kind of hard to get to via their site, not because it's a great phone or anything):
In addition to this topup promotional, the phones sell for the same or less than on VirginMobileUSA.com.
Kyocera K10 Royale - $49 vs. $50 on VMUSA
Nokia Shorty - $40 at both places
Audiovox V7 Flasher - $100 at both places (cheap prepaid camera phone)
Audiovox Vox - $70 vs. $90 at VMUSA (you save $20!)
Plus you get the $20 top-up card. So if you got the Vox you'd be saving $40 over purchases elsewhere. With the other phones it's $20, which is still nothing to sneeze at.