The easiest way to read from SPSS is accessing the foreign library and using the read.spss command.
In R type:
library(foreign)
newdata <- read.spss("c:\\temp\\data.sav")
attach(newdata)
You will get a warning, but this doesn't seem a problem. All the variables will be in UPPERCASE. R is case sensitive so group and GROUP do not mean the same thing. read.spss does not handle all missing values well. If there are value labels for a variable in SPSS, R reads this as a categorical variable.
The the foreign library also allows data to be read from other packages (like Minitab, SAS, Stata, Systat) and writing to these packages. The paper does not use data from SPSS, but this page was included because is popular among psychologists.