Hi Shane,
The Google sandbox is really a theory or effect about what happens to new sites, or sites that have a bunch of different ownerships in a short time frame that aren't doing well in the search engine listings. In short what Google does supposedly, is place these sites in a holding area until the sites establish somekind of authority or prominence.
BUT, Google doesn't claim or acknoledge that it has a sandbox or that the sandbox effect exsists at all. This is why it is basically a theory for now.
The best way I know of to tell if you've been sandboxed is if your new site was listed high in the results for specific keywords or keyword phrases, then plummited down the result pages further for these keywords and phrases, or simply out of the results completely.
To double check to find out if you site has been put in the box, pull up Google search page, and type
site:yourdomain in the search box and click enter on your keyboard. This will let you know real quick whether you still have pages listed in the serps or if it's in the box.
To get out of the box it will take some time though, usually a couple of months or so. The best thing to do in my opinion is to get as many high quality backlinks as you can to you site while it's there, and update your site as much as you can with high quality original content. This will prove to Google that the site is worth bringing out.
You can get backlinks in various ways. Here are a couple that I use frequently:
1) Through articles
2) Relevant blogs and forums
3) Directories (bigger ones with
PR if possible)
4) Ask site owners to swap links
5) RSS feeds (Get your feed out into as many RSS directories as you can)
Hope this helps ...