RapidWeaver Classic doesn't have online editing capabilities built in. However, there are plenty of plugins and stacks that allow you to build a blog or site with online editing capabilities.
Here are a complete list of CMSs compatible with RapidWeaver.
Alloy from Elixir Graphics (Blog focused)
EasyDB / Dynamic Content from Stack-Its
WebYep stack from Stacks4Stacks (WebYep is open-source)