Perhaps a year back I read from a local news paper that purified gasoline cleans out very well the glue residues from several materials. That tip has proven to be quite usefull. What I do is that I soak the jar in a soapy water until the label either falls out or is completely wet and soft. Then I remove the label by peeling it with my nails. Then I take piece of paper or cotton wool and dampen it with purified gasoline. Then I wipe the glue residue off the jar. The gasoline evaporates quite fast so you might need to add it a few times. When the glue is removed the jar feels slightly oily from the gasoline and it needs to be cleaned off with dishwashing liquid.
Finished! In Finland the purified gasoline can be bought from the pharmacy. I have been thingking of using just regular gasoline for the purpose, I'm intriqued if that would work as well. Do you have any other tips on how to remove the labels from containers?