The economic stimulus package increased the FHA loan limits in most part of the country. In the most expensive areas of the country FHA loans can be up to $729,000 in 2008. But those limits expire at the end of 2008. The new maximum limits (as a result of the newly passed housing legislation) will range from $271,000 in lower cost areas to a maximum of $625,000. The limit is calculated by multiplying the median housing price in a county by 115%. (The conventional loan limits with Fannie Mae and Freddie Mac have the same upper limit but have a $417,000 low end no matter what the median housing price is in a county.)
See here to search current FHA loan limits by county.