Hi, Is there a way to do Vertex Blending in OpenGL (see this page if you don't know what Vertex Blending is). And if it exists, is it just an extension or is it widly supported?

I haven't done it myself but yes you can.
It's also called vertex skinning or vertex weighting AFAIK.
You can provide several model view matrices and blend them together with vertex blend weights. Either you do it using the vertex weighting extension or a vertex program. Both should be widely supported meanwhile. (E.g. vertex programs are supported even on my old GF2 MX, though running in software emulation mode)