I've just uploaded a new release of RMagick. This release fixes 3 bugs, including a memory leak in the ImageList#to_blob method. If you're using this method in your programs you should upgrade.
As usual, RMagick is available at RubyForge: http://rubyforge.org/projects/rmagick/
RMagick is an interface to the ImageMagick (http://www.imagemagick.org) and GraphicsMagick (http://www.graphicsmagick.org) image processing libraries.