A man has posted a page claiming to be building a solar power forge that can heat steel to over 1000 °f, hot enough to get it red hot and forge it. He used a home made parabolic mirror to heat steel instead of the traditional gas, coal or charcoal furnace. The idea of a solar powered forge is attractive in the developing world where fuel is scare and deforestation is a huge problem. There is quite a bit of doubt over his claims. People doubt that a mirror could be practically built large enough to capture the required sun to heat steel to the correct temperature and keep it correctly aligned as the sun move across the sky. Another issue is the size of the area being heated being large enough to practically work steel. But the idea is very interesting. Even if he can not get temperatures high enough from his Solar Power Forge for metal work, there are plenty of other interesting applications in heating and cooking.
He has posted detailed instructions and plans and fully discusses his project and addresses doubt over his claims.
Here is the link to the page.