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http://www.cdc.gov/vhf/ebola/outbreaks/guinea/index.html

Current outbreak appears to be around 50-55% mortality.

According to More or Less, 90% was the mortality rate of one particular historical outbreak.

http://www.bbc.co.uk/podcasts/series/moreorless

http://downloads.bbc.co.uk/podcasts/radio4/moreorless/moreor...

edit - It also says that 52% is the current figure on this outbreak and that if you count up all cases, then Ebola has a mortality rate of 60-65%.

It varies by subtype.

Indeed. There were 5 classified types prior to this outbreak: https://en.wikipedia.org/wiki/Ebolavirus#Classification

With the Zaire strain, now just called plain Ebola virus, normally with an observed fatality rate of 83% or 76% (two figures from different Wikipedia articles) and up to 90%, and at the other end a Reston ebolavirus with no fatalities among exposed lab workers.

This West African outbreak has been sequenced and is a Zaire strain with plenty of mutations that perhaps have significantly dropped its fatality rate, see this section and the following: https://en.wikipedia.org/wiki/2014_West_Africa_Ebola_virus_o...