I am sending out a survey and want to include a standardized five factor inventory. I believe I may increase my response rate if I use an instrument with less than 60 items, but I do not want to sacrifice validity and reliability.
Have you seen The TIPI is a 10-item measure of the Big Five (or Five-Factor Model) dimensions?
See the following article for more details
Gosling, S. D., Rentfrow, P. J., & Swann, W. B., Jr. (2003). A Very Brief Measure of the Big Five Personality Domains. Journal of Research in Personality, 37, 504-528.
You will almost inevitably suffer some loss of reliability (and of course validity). After all, the NEO-FFI is a carefully constructed measure; if the authors could have achieved better results with fewer items, they'd have done so. As it is, you have only 12 items per scale!
However, shorter versions do exist. You could use scales provided by the International Personality Item Pool (IPIP; see link below). These include 10-item measures of each of the Big Five traits, so you'd reduce the length from 60 to 50 items. Reliability data are quite good for the IPIP scales, though to my eye they sacrifice breadth of coverage in the pursuit of internal consistency.
There is also a 10-item instrument that attempts to measure all five traits. As you would expect, this definitely sacrifices a fair amount of reliability, but it can be useful if you're running a very large-scale study. Again, see the link below.
Both of these are available free of charge to all interested researchers.
There is also an instrument called the Big Five Inventory (John & Srinivasta, 1999). It's 44 items in all. I think the data are pretty good for it, but I'm not 100% sure. I'll attach a copy.