If you have been banned from the network after clicking on one of these links, please email firstname.lastname@example.org with your internet-routeable IP address. Visit http://myip.dk/ and include both the IP address and hostname provided on this site. It's also helpful if you let us know what nick you were using at the time. We will address these requests as quickly as possible, but please be patient.
It is of course never a good idea to visit a link that's not from a trusted source. If you must do so, look into using a browser with limited or no scripting support (wget from the command line is a great solution here on linux, as is links) or using something like no-script for firefox.
If you run a channel on freenode, you might want to consider setting +R to prevent unregistered users from sending to the channel as the spambots described here will not be registered. If you do so please consider being proactive about contacting unregistered users joining your channel to ensure they get the help they need, and feel free to send them to #freenode so network staff can help them register.
For users, now is an excellent time to register your nickname and setup your client to auto-identify. You can find information about registering here. Configuring your client to auto-identify varies depending on the client, but one easy way is setting up your client to send the nickserv password as your server password. Most clients have an option for this.
It is also worth noting we will be moving to a new ircd in just 13 more days, as described here. This new ircd provides a number of exciting new capabilities including improved capability to deal with spam of all kinds, including this most recent type which is entirely mitigated by improvements in seven.