Low range estimate: 1.4 g CO2 equivalent per kilowatt hr
Mean estimate: 66 g CO2 equivalent per kWh
High range estimate: 288 g CO2 equivalent per kWh
This is from a metastudy of 103 studies
You can access the full text from this page on the Nuclear Information and Resource Service
Here is a link to the PDF: Sovacool, B. K. 2008. Valuing the greenhouse gas emissions from nuclear power: A critical survey. Energy Policy v. 36 (8): 2950-2963.
For comparison, a natural gas-fired power plant might emit 515.29 g CO2 per kWh (per wikipedia: http://en.wikipedia.org/wiki/Fossil_fuel_power_station#Carbon_dioxide; (conversion to metric mine & therefore mistakes are as well.) Coal and Oil-fired plants will emit more CO2 than a natural gas plant.
ETA: After more thorough checking, confirmed the neighborhood for CO2 equivalents emitted throughout the life cycle for natural gas and coal plants from Jarmillo et al. "Comparative Life-Cycle Air Emissions of Coal, Domestic Natural Gas, LNG, and SNG for Electricity Generation" in Environmental Science and Technology from 2007, link: http://www.ce.cmu.edu/~gdrg/readings/2007/09/13/Jaramillo_ComparativeLCACoalNG.pdf
Natural Gas midpoint: 499 g CO2 equivalent per kWh
Coal midpoint: 953 g CO2 equivalent per kWh
These are close enough to the wikipedia figures (although not exactly the same) that it appears wiki is also using the lifecycle emissions. Again, the conversion to metric is mine & etc.
A lot of science and policy work treats nuclear power as having 0 CO2 emissions, but that's not quite true, and especially is less true if the higher emissions numbers are more correct.