Data is very large indeed, must all data be processed at once. Or can you attempt to use some cross validation techniques etc. If this is not possible, there are a few tricks, which includes increasing page memory on your machine to accommodate for larger matrices, but will dramatically decrease the speed of computation due to constant access to hard drive for data. Good luck.

classify by Weka

classification techniques as Mohammad mentioned

Mahout has some algorithms (other than NN) for classification. There are some large matrix operations. Check if they solve your problem (http://mahout.apache.org/).