Diaries and posts allow a relatively restricted subset of HTML, including these tags:
<a> <i> <b> <tt> <ol> <ul> <li> <p> <div> <strong> <em> <cite> <blockquote> <br> <pre> <dl> <dt> <dd>
In addition, there are special, Advogato-specific tags. Type <person>foo</person> to link to foo's diary page. You can similarly type <proj>Project</proj> and <wiki>WikiEntry</wiki>.
New HTML Parser: The long-awaited libxml2 based HTML parser code is live. It needs further work but already handles most markup better than the original parser.
Keep up with the latest Advogato features by reading the Advogato status blog.
If you're a C programmer with some spare time, take a look at the mod_virgule project page and help us with one of the tasks on the ToDo list!