Installed Apache, configured your DNS but STILL having trouble accessing your domain at slicehost? You probably need to adjust your iptables (firewall) rules.
This article really helped me understand iptables at a very basic level. It's been a couple of years since I really delved into linux and things have become really nice.
I also found out that slicehost correctly configures your firewall pretty tight, allowing new connections for ssl only. Wow, another thing done right at slicehost!