You can set up a custom domain using Posterous. Here’s the skinny:

1. Find a domain you like using Instant Domain Search. Most great domain names are taken, but there are a few gems out there left yet.
2. Register your domain using Go Daddy or register.com. This should usually cost about $10 per year. Avoid the extra fees around website hosting, and other services. All you need is a Domain Name Registration, probably for the period of 2 years.
   Using GoDaddy? See below for some additional screenshots of how to configure your domain.
3. Create an A record from the desired internet address to the following IP address hosted by Posterous: 67.207.139.81
4. Click Manage » Edit Site to set your custom domain to www.yourdomain.com.
5. You’re done!