There do seem to be some funky things going on with that site. It seems to return no data unless you fake the user-agent. Even then, readHTMLTable doesn't behave too well, returning an error if you pass it the whole doc. After reading the source, you can see that the relevant table has id table_results_r_1 and isolating that and passing the result through works:
library(XML)
library(httr)
theurl <- "http://www.rout.gr/index.php?name=Rout&file=results&year=2011"
doc <- htmlParse(GET(theurl, user_agent("Mozilla")))
results <- xpathSApply(doc, "//*/table[@id='table_results_r_1']")
results <- readHTMLTable(results[[1]])
rm(doc)
Now you'll need to tidy up the table column names.