Given the current market conditions with foreclosures at an all-time high, this question is being asked exponentially more than it was just a few years ago. While it is often said that you can't buy for 7 to 10 yrs, this simply is not true. 

While a foreclosure is extremely detrimental to your credit, it doesn't preclude you, for often times no more than a few years.

How long before you are eligible for another mortgage depends on a few factors. Mainly: what your credit looks like post-foreclosure. If you have kept all your bills current, and your credit card balances low, you will see your credit slowly move up towards the 600's within a few yrs after the foreclosure. 

If you continue to pay your credit cards late and keep your balances high, you will be in no better shape a few yrs after your foreclosure, compared to immediately after.

Every bank is different

Banks are constantly changing and updating their lending criteria on a day-to-day basis. So, while a few years back, one could be a year or two out of foreclosure and still get a loan.  Now, it has become increasingly more difficult as the credit markets have dried up.

What if I have solid credit (600-700 FICO) but I have a foreclosure a few yrs back?                          

As mentioned before, it really depends on the bank. However, if you have a foreclosure and a 650 credit score, for example, do not expect to get the same treatment, as someone with a 650 and no foreclosure. While a FICO score is important and the impact of a foreclosure on one's credit will slowly wane, some banks--regardless of credit score--have a specific period of time before they will lend to someone that has defaulted on a mortgage. 

If you can avoid foreclosure through a short sale, short refinance, or a loan modification, it is typically in your best interest to do so. A foreclosure will remain on your credit for up to 10 yrs, and even as your FICO score improves, the scarlet letter of a mortgage default is the first thing that a potential lender will see when examining your credit.