This site is responsive on my cable connection, but maybe this has something to do with the fast hosting service.
I have been optimizing a dynamic website for my company because modem users have been complaining about long load times. I altered the sourcecode and dropped the generated-HTML filesize (on the page that was the most troublesome) from 100k to 65k just by eliminating the extra whitespace.
I downloaded the sourcecode for this thread, and it was a 106k textfile. Simply stripping out excess tabs and spaces dropped that to 93k. My guess is that the server is told to output text to the browser exactly as it is typed into the sourcecode, whitespace formatting and all. So, for a 10% increase in speed, I recommend that an administrator go to the site's tag generating code and remove any whitespace characters where the code tells the forum software to directly output HTML tags.
Example (I don't know phpBB syntax):
<!-- print directly to browser -->
<table>
<tr>
<td>
<td>
</tr>
</table>
<!-- now go back to the script -->
Should be:
<table><tr><td><td></tr></table>
Another thing: what about putting all the stylesheets data into a separate .css file (the same goes for the javascript)? Then the browser can cache that data and not reload it with every page.
And finally, I'm not sure if this is my browser's (IE6) fault or what, but many of the links seem to have an "absolute" address, rather than a "relative" address. Example: Flag: <img src='http://www.hydrogenaudio.org/html/flags/blank.gif' align='top' border='0'>
could be Flag: <img src='/html/flags/blank.gif' align='top' border='0'>
All other optimizations would require a lot more work. For example, any properties that's applied to all <td>'s could just be applied once to a <tr>. And then there's the option of throwing out all the table tags and switching to pure CSS layout... (I've toyed with that on my site... waaaay too much work! Going from tables to CSS for layout is like learning how to walk again! )