Some people may receive calls or emails from department heads, firm management etc, indicating they are needed and wanted in their practice groups. In that case, of course show up.
If you are a summer this year and your firm has already delayed start dates, you ask what does that mean? Well, as I said before, firms are going to be VERY careful about giving offers. Firms did overhire (not all but some) because many engaged in standard recruiting and didn't quite determine how dire things were till the end of 08. As such the classes coming into summer are larger than if they were doing the hiring now. Will there be further push back of start dates? Well that is unclear - after all, this is all new - really, unprecedented. The formerly fall 09 people are now winter 2010. So, do I think firms will be ready to absorb fall 2010 people? If the economy stays slow, probably not. I think firms will be very tight with the offers this summer and are going to watch to see how things go.
Someone asked whether they should go ahead with on campus recruiting even after summer 09 and if they have an offer. I don't see anything so wrong about that. I think firms will understand that people may need to see what is out there. They are not loyal, so why should you be. Try to be discreet. Remember, you need to look out for yourself.