I had an external drive connected and deleted some of the files. I disconnected it without emptying the trash. I just realized that I never emptied the trash. Now when I try to delete, finder either locks up or if I run "rm -rf /Volumes/External/.Trash" it says directory not empty. No matter what I tried, it won't delete.
How I ended up deleting it was:
I plugged it into a Windows 7 machine and the folder (.Trash) was right there in the root of the drive.
Right Click -> Delete