If you have to deal with tilde’s in url’s, RedCloth messes them up but good.
The fix is simple, yet annoying - go to the redcloth.rb file (normally located in /usr/lib/ruby/gems/1.8/gems/RedCloth-3.0.4/lib/ or /usr/local/lib/ruby/gems/1.8/gems/RedCloth-3.0.4/lib/, and apply the changes in the above changeset (basically, add a :limit clause to each tag).
imagemagick required.
for file in *.jpg; do
thumb=`echo $file | sed s/.jpg//g`_s.jpg;
cp $file $thumb;
mogrify -thumbnail 900x100 $thumb;
done;