My rationale when I was dealing with this problem was that if whatever I was doing became successful, I'd be able to get for the domain name from the squatter. In the meantime, your options are:
1. Register a non-.com domain such as .co, .io, etc. I would avoid .org, because that I think that was originally created for non-profits.
2. Use a variation on your intended domain name like "hq", "my", etc. Dropbox started with getdropbox.com, and Square originally used Squareup.com.
3. Use a domain hack like "bit.ly", "del.icio.us", etc. I'd personally would rather not try to artificially cram my company name into a domain hack, but if it fits then go for it.