Tonight there will be a Panel on PHP Scalability at geeksessions.com which you can catch streamed at justin.tv. The panel for this is full of some serious heavy hitters but unfortunately I’ll be in class while it’s going on but will definitely catch it when they post archives. These guys show how PHP is used by some the biggest companies on the web.
Another nice thing is the the moderator for this panel will be Terry Chay, who’s blog I really enjoy, especially for a good Ruby rant (Warning, there are occasionally bad words 
). I look forward to catching his talk at PHP|tek this May.
Also might want to catch the 1.2 geeksession that is on there as well, again another group of big guns.