ChangeLog (brief summary of your edit for later reference):
No HTML.
A line begins with ";;" doesn't appear in the output (comment).
A line begins with "~" is treated as if it is continued from the previous line, except comments. (line continuation).
Empty line to separating paragraphs (<p>)
"- ", "-- " and "--- " ... at the beginning of a line for an item of unordered list (<ul>). Put a space after dash(es).
"# ", "## ", "### " ... at the beginning of a line for an item of ordered list (<ol>). Put a space after #'s.
A line with only "----" is <hr>.
":item:description" at the beginning of a line is <dl>. The item includes all colons but the last one. If you want to include a colon in the description, put it in the next line.
[[Name]] to make "Name" a WikiName. Note that a simple mixed-case word doesn't become a WikiName. "Name" beginning with "$" has special meanings (e.g. "[[$date]]" is replaced for the time at the editing.)
A URL-like string beginning with "http:" becomes a link. "[URL name]" becomes a name that linked to URL.
Surround words by two single quotes (''foo'') to emphasize.
Surround words by three single quotes ('''foo''') to emphasize more.
Surround words by three double quotes ("""foo""") for fixed-length typesetting.
Surround words by three tildes (~~~foo~~~) for strikeout.
"*", "**" and "***"' ... at the beginning of a line is a header. Put a space after the asterisk(s).
Whitespace(s) at the beginning of line for preformatted text.
A line of "{{{" starts verbatim text, which ends with a line of "}}}". No formatting is done in verbatim text. Even comments and line continuation don't have effect.
A line begins with "||" and also ends with "||" becomes a row of a table. Consecutive rows forms a table. Inside a row, "||" delimits columns.
"~%" is replaced for "<br>".
If you want to use special characters at the beginning of line, put six consecutive single quotes. It emphasizes a null string, so it's effectively nothing.