I notice that /usr (/dev/sda2) is at 96%. ext2 has some pretty bad problems with fragmentation once it gets above a certain percentage. This can cause some pretty bad performance problems. Once it has fragmented, it is difficult to get it back to a contiguous state.
There are defrag programs, but they are fairly scary. The only other way to get it back to normal is to back everything up, mkfs, and restore it.
Perhaps somebody can remove a bunch of the packages that are installed that we don't use?