If you want to publish your own anonymous site, see Upload a Freesite. The list of indexes uses dynamic bookmarks. You get notified whenever a bookmarked site (like the indexes above) gets updated.
You can create additional IDs at any time and give them any name and legend you choose by adding it on the WebOfTrust-page. Each new ID has to verify for itself that it's human, though. If you carefully keep them separate, others can only find out with a lot of effort that your IDs are related. Mind your writing style. In doubt, keep your sentences short. To make it easier for you to stay anonymous, you can autogenerate Name and Legend at random. Don't use the nicest from many random trials, else you can be traced by the kind of random IDs you select.
If you want to use an existing name, be aware that this will make your anonymity depend on any other service where you used the same name. If some people can trace your name on a single one of the other services, they can perform a lexical analysis of your writing style to verify that your name in freenet and on the cracked service belongs to the same person. Only use an existing name, if the anonymity of that ID is not crucial.
Note: If you download content from freenet, it is being cached by other nodes. Therefore popular content is faster than rare content and you cannot overload nodes by requesting their data over and over again.
You are currently using medium security in the range from low to high.
In this security level, separated IDs are no perfect protection of your anonymity, though, since other members might not be able to see what you do in Freenet, but they can know that you use freenet in the first place, and corporations or governments with medium sized infrastructure can launch attacks which might make it possible to trace your contributions and accesses. If you want to disappear completely from the normal web and keep your freenet usage hidden, as well as make it very hard to trace your contributions, to be able to really exercise your right of free speech without fearing repercussions, you can use Freenet as Darknet - the more secure but less newcomer friendly way to use freenet; the current mode is Opennet.
To enter the Darknet, you add people you know and trust personally as your darknet friends. As soon as you have enough trusted friends, you can increase the security level to high and freenet will only connect to your trusted friends, making you disappear from the regular internet. The only way to tell that you are using freenet will then be to force your ISP to monitor all traffic coming from your computer.
And once transport plugins are integrated, steganography will come into reach and allow masking your traffic as regular internet usage, making it very hard to distinguish freenet from encrypted internet-telephony. If you want to help making this a reality in the near future, please consider contributing or donating to freenet.