On my own forums I just ban IPs from certain countries known for spamming, but that that's not as international as this forum, so that woulnd't be fair.
The other way is to use a plugin that ties in with StopForumSpam or similar, but that's no perfect as it relies on other forums reporting those spammers in the first place.
Considering the measures that have been put into place (no URLs, no PMs, etc.), I think the moderators are doing a reasonable job of controlling the spam. Spammy posts are usually cleared up within 24 hours of posting (although I do think having a couple of mods across the timelines would be helpful). Really the only next step that could be taken is to manually moderate each new user's first post (and preventing them from posting further until it's been done), but that can quickly become a heavy workload, and isn't all that friendly for legitimate new users.
EDIT: I'll add that spammers seem to sometimes put their URLs in the heading of the post, so that should probably be included in the spam filter.
Also, I guess that this post should be in Forum Issues, but at least it's getting some attention here.