There doesn't have to be a total economic collapse.
If we invest in the right directions including public transportation, electric cars, and renewable energy resources then new jobs will be created and the economy can grow. Also in the U.S. the internet is becoming so huge that I think we will adapt or have to adapt to working more at home.
Now food production will be the hardest thing in the future, especially since almost all fertilizers are made from fossil fuels.
Energy is going to be the largest problem for the next 20 years though. The oilsands, drilling off the coasts, the oil shale, etc. will not be enough if we reach peak oil in the next couple years. The Department of Energy has a great study on why these won't be enough which is linked to below.
Why won't the oil shale be enough if peak oil is reached now or within the next 3 years?Answer: The oil shale production is only supposed to amount to about 1 million barrels per day in 2015, and they're still not sure if they can get more oil out of the shale than energy they use!! (negative EROEI which won't matter if it is ever cost effective)
Oil sands production if it is ramped up at the fastest rates is only supposed to amount to 3.5 million barrels a day in 2015 from about 1 million barrels a day now!!
Opening up Alaska is only supposed to add 1 million barrels a day by 2015!!
Oil production is probably at its peak now. Oil production which includes the oil sands, heavy oil, all sources has been on a PLATEAU for almost the last 2 years now at about 84 million barrels a day. This is the real reason that oil prices are so high. Believe a picture is worth a thousand words than look at this picture of the oil production figures from the last few years and the PEAK developing(it is the second chart down, the first shows that Saudi Arabia is probably peaking right now!):
http://www.theoildrum.com/story/2006/7/2/205758/5414#more
Do I think we shouldn't produce Alaskan oil, the oil sands, oil shale, etc. because each individual thing won't solve the problem? Hell no, we need to do them all. We need to rape the earth if we have to, but we do need to attempt to rape it gently

Such as using carbon sequestration technologies for all new coal to oil production.
The people that think the energy crisis coming won't be a big deal because of this or that, need to do more research because frankly even President Bush and Cheney know this coming energy crisis is going to be huge.
Here is the
Department of Energy study which is a great place to learn why the energy crisis coming will be a big deal:
http://www.netl.doe.gov/publications/others/pdf/Oil_Peaking_NETL.pdf
This study above and the one posted by Caliginousface from the Army Corp of Engineers are must reads if you are a doubter that an energy crisis is coming.
Caliginousface, Please post some on EROEI. It is one reason making ethanol from corn is barely worth our time. We need to be making it from switchgrass and other sources. Also we need to start making cellulosic ethanol a reality.
Jet