The latest information from management on the impairment of service:

We are still working to contain the ongoing DDoS attack, and to this end we have recently upgraded our service with Rackspace. This should restore access to our readers who have been blocked for the last week. However, some users may still be blocked, so please continue to send blocked IP addresses to webmaster@scienceblogs.com (or have them send us their IP addresses directly). As a preventative measure, please send your own IP addresses as well; we will add these addresses to Rackspace’s whitelist.

The problems should start easing up. If not, harass the admin at the address above.