Download apps from getjar.com
They tell you you can download apps from www.getjar.com but i have tried several times and can't download a thing other wise i love it.
Update 2013: You now need to go to m.getjar.mobi to download J2ME apps.
Yeah, I can't figure out what's going on with the getjar site. It doesn't seem to recognize the phone. When I go on to getjar.com via my laptop, I can set my phone to the LG 900g, and it recognizes it, but when I go to download an app to the actual phone, their mobile app says that it is unable to recognize the phone. You may be able to download it to your computer and transfer it to the phone, though I haven't tried that.
Does work with other mobile apps sites
What I have been able to do is download games and apps from other mobile apps sites. For example I downloaded a Tetris clone (not a good clone unfortunately) from the sharejar.com site. I went to the site first with my pc and found the app I wanted. The site lists a WAP code. Then you go to sharejar.mobi and click on the Quick Download link, enter the WAP code and download your app or game. Once downloaded to my games directory, I was able to launch and play the (not so good) game.
Similarly, you should be able to find other sites to download apps for Net10 phones.
Hope this helps.