The best deal has got to be the LG Optimus Slider Android QWERTY slider Android QWERTY for $19.99. The Slider was priced at $149.99 when it was launched in Sept, 2011 and was selling for $129.99 a week or so ago. It's getting a little dated but is still a good phone. The keyboard is probably the best of any of Virgin's Android QWERTYs, the phone is rugged and stable and the camera is pretty decent.
The only real downsides to the Slider are that there isn't much internal storage for installing apps and that it's unlikely to ever be upgraded beyond Android 2.3. Still, it's a great backup phone and it's one of the handsets that users on Virgin's grandfathered $25 and $40 grandfathered plans can switch to and keep their current pricing. The $19.99 price is good until Jan. 3rd but I expect it to sell out long before that.
Update: The slider sold out in a couple of hours. Possibly more will show up before the sale ends on Jan 3rd.
Among the better deals that are still available, The 79.99 LG Optimus Elite Android phone $79.99 (reg $129.99) is another phone that will let you keep your grandfathered status. It's not a QWERTY but has plenty of room for apps and a bigger screen and better camera than the Slider
If you aren't grandfathered or are OK with losing grandfathering, the $49.99 Kyocera Rise is an Android QWERTY slider that runs Android 4.0 Ice Cream Sandwich and doesn't have the Optimus Slider's memory limitations either.
The other phones and mobile broadband devices on sale at virginmobileusa.com are listed below:
Ovation MC760 3G USB stick modem $9.99 (reg $49.99)
payLo Samsung Entro flip phone $11.99 (reg 14.99)
payLo Kyocera S2100 flip phone $15.99 (reg $19.99)
payLo Kyocera S2300 QWERTY candybar $15.99 (reg $19.99)
LG Optimus Slider Android QWERTY slider $19.99 (was $129.99)
PCD Venture QWERTY candybar $19.99 (reg $49.99)
Novatel MiFi 2200 3G wireless hotspot $19.99 (reg $99.99)
payLo Samsung M575 QWERTY slider $39.99 (reg $49.99)
U600 3G/4G USB stick modem $39.99 (reg $69.99)
payLo Samsung Montage QWERTY slider $39.99 (reg $49.99)
Kyocera Rise Android QWERTY slider $49.99 (reg $99.99)
PCD Chaser Android phone $49.99 (reg $79.99)
LG Optimus Elite Android phone $79.99 (reg $129.99)
Overdrive Pro 3G/4G wireless hotspot $79.99 (reg $119.99)
Samsung Galaxy Reverb Android phone $99.99 (reg $149.99)
HTC One V Android phone $99.99 (reg $149.99)
HTC Evo V Android phone $189.99 (reg $279.99)
Motorola Triumph Android phone $199.99 (reg $279.99)
Samsung Galaxy S II Android phone $329.99 (reg $369.99)