There are more materials, but the bulk of overall materials is in the infrastructure, not manufacturing, unless we're destroying and rebuilding our manufacturing line every year. ;) Transmission is almost all Al/Fe. For steel news on biocharcoal seems to be picking up a bit, although it's not receiving a lot of publicity since coking coal isn't going to be in short supply any time soon, compared to oil at least. Indium is used in thin film panel manufacturing, specifically in CIGS, but thin film is only projected to capture ~30% of the market by 2012, and has been and will represent the minority of panels produced for a while. Even then, it's not like we can't make solar panels w/o Indium, just that at the moment they appear to be the cheapest, at least in bulk, with thin film Silicon not too far behind IIRC. While Indium may present a limit to CIGS based thin film, solar panels in general do not require it, it just happens to allow for the cheapest manufacturing at the moment.

Besides, saying that solar PV is a limiting factor in sustainability because it uses limited resources is kind of pointless since the sun's useful lifespan is also limited for the same reason. I mean, when looking at sustainability, we should be looking at likely (and present in some cases) limiting factors, not trivial ones. Sure, we can't have an infinite number of solar panels, just like we can't have an infinite time with the sun as it is now, but neither one is a meaningful limiting factor in terms of sustainability, at least not yet. If we manage to get to that point that they are likely limits whenever in the future I'll happily concede the fact, but as of right now we have thousands of years worth of other crap that'll provide a limit far sooner than solar panels, or for that matter the sun's lifetime, will.