Since you have an Intel Mac, and they don't have a download link (technically they do, but it requires a proprietary Windows-only program), you really only have two options:
1) Wait for the Flip4Mac WMV codec that Microsoft has licensed to get out of beta (which should be pretty soon), then install it and it'll work fine.
2) Install the older, PowerPC-only version of Flip4Mac, then run your browser (and I maybe Quicktime too...?) in Rosetta. I haven't tried this, so you'll need to look elsewhere for instructions (they've been posted here several times over the last couple of weeks), but it should work.
Personally, I'd just do #1--it should be out pretty soon. Also note that if you install the free PopWire WMV codec right now, you can at least play most downloaded WMV files (the free VLC player will play almost anything else), but it doesn't do embedded WMV.
The ironic thing about that particular site is that the "embedded" player link they give you is a completely self-contained Flash player, so it will play just fine on any Mac. In fact, if you just copy the part that starts with "http" and ends with ".swf" from that box into a browser window, you'll get a full-window-sized player that should work perfectly without having to install anything new (if it doesn't download and install the latest Flash player from Adobe).
It's a bit of a hassle, but if you need your like metacafe video, it'll stave you off in the mean time.
No idea why they offer an embedded Flash player, yet force you to use WMP on their site...
