The sandbox, which has to do with rankings is different from being indexed, which has to do with Google knowing about your site. Submit your information to Google sitemaps and they will pick up the rest of your pages. If you have a penalty or something like that, they will let you know. The sandbox is not a penalty BTW, it is a side effect of their ranking algorithm.
My sense is that Google themselves don’t really know themselves exactly how to get out of the sandbox. Having met with some Googlers over the past few days, it’s a bit more clear that the algorithm they have has hundreds of aspects to the formula, many of which PhDs have come up with. So you can imagine just how complex the thing is. This sandbox effect has come out of the updated algorithm, and really the SEOs are probably the better one’s to ask as to how to get out.