Check to make sure the site resolves. Then try to perform a tracert (or traceroute for Linux and Genesis, miamitraceroute for Miami.) You can also try connecting directly to port 80, try other computers in the same network or using the same Internet connection.
Here's my nslookup:
Non-authoritative answer:
Name: amiga.org
Address: 174.132.193.125
Aliases:
http://www.amiga.orgIf it doesn't resolve on your end, try using DNS servers other than what your ISP provides, like OpenDNS or Google DNS.
If your ISP is blocking AO and they won't fix it, take your business elsewhere if you can't defeat the block.