Mark,
I believe a change has come about with the site software since the crash the other day. The attachment links contain a "?" now, such as
http://www.treebuzz.com/forum/download.php?Number=21673 and I'm pretty sure they had not before. I may be wrong about that, but in any event, apache's (the HTTP server software) "mod_rewrite" module can be used to provide and use links which do not contain the "?" for data which really should be static in nature. The significance is that such links are direct queries of the database and by their very nature (since the result is forever a "new" entity) they are not cacheable and web caches will not even store them as they pass through.
I bring this up because, as you know, I'm held captive behind a modem, so I use a web cache this side of it. If the entity could be cached, so long as disk space and the entity's time-stamp hold out, subsequent requests would be provided from the web-cache instead of over the wire. As it currently stands for me every time I visit a thread here and wish to view an attachment, it must come from the server at about 5 kB/s instead of the web-cache at the 10 MB/s it
could.
Many segments of the Internet are behind such caches used to curb bandwidth needs upstream, and they too would benefit, not to mention your server bandwidth would decrease as well. Maybe you're not paying for your bandwidth on a metered basis, but if you are, the few bucks invested in having your admins set this up would be recovered eventually, and many of your visitors would have a better experience.
Same goes for apache's "mod_gzip", which would send text data compressed, usually at about 80:1.
Just some suggestions...
Glen