These cost money and free versions can be found but it's still good to have, plus it's a good thing to do to support these guys.

http://www.haymarketbooks.org/Merchant2/merchant.mv?Screen=PROD&Store_Code=Haymarket&Product_Code=MS1903&Category_Code=MS
(don't bother looking for a free english version of that one)

http://www.haymarketbooks.org/Merchant2/merchant.mv?Screen=PROD&Store_Code=Haymarket&Product_Code=MSIHS&Category_Code=MS
(a Very important book)

http://www.haymarketbooks.org/Merchant2/merchant.mv?Screen=PROD&Store_Code=Haymarket&Product_Code=MSEL&Category_Code=MS
(several must reads for any Leninist in there)

http://www.haymarketbooks.org/Merchant2/merchant.mv?Screen=PROD&Store_Code=Haymarket&Product_Code=MSLFF&Category_Code=MS
(some of those cannot be found free in english- first time in engish, just like the first one)

http://www.haymarketbooks.org/Merchant2/merchant.mv?Screen=PROD&Store_Code=Haymarket&Product_Code=MSMSR&Category_Code=MS

http://www.haymarketbooks.org/Merchant2/merchant.mv?Screen=PROD&Store_Code=Haymarket&Product_Code=MSLA&Category_Code=MS

http://www.haymarketbooks.org/Merchant2/merchant.mv?Screen=PROD&Store_Code=Haymarket&Product_Code=MSTDS&Category_Code=MS
(Not by Lenin but possibly the best account of the Russian revolution and the time following I've read)