Walmart.com has a couple of Virgin Mobile's better Android phones on sale at very good prices. The LG Optimus Elite and the LG Optimus Slider are both marked down to only $99.88. The Elite's regular price is $149.88 and the Slider normally goes for $162.88.
Unless you absolutely require a hardware QWERTY keyboard, I recommend the Elite over the Slider. It's a newer model with a bigger screen, better camera and more internal memory for app storage. The Elite has a faster processor too. The specs say both phones have an 800 Mhz CPU, but benchmarks show the processor speed is actually 1 GHz! Not bad for a $100 phone. You can compare the two phones specs on GSMArena.com.
Update: both phones have sold out online