The download page http://poi.apache.org/download.html has this link under "Source Distribution": http://www.apache.org/dyn/closer.cgi/poi/release/src/poi-bin-3.10-FINAL-20140208.tar.gz Note the "poi-bin" part. When I click that link, it gives me a bunch of mirror links, all with "poi-bin" in them, and all broken! If I change "poi-bin" to "poi-src", it seems to work.
Good spot, typo fixed in r1572482, and should be live on the site shortly