I was just writing about the data mining tool RapidMiner on my AI blog. RapidMiner is based on many open source projects for machine learning, clustering, data access, and data visualization, so a lot of developers contributed to that 25 megabytes of compiled Java code :-)

For comparison, NetBeans 6.0 seems to use about 15 megabytes of compiled code and Eclipse weighs in at about 100 megabytes.