I would like to offer a cartoonist's context (sorely missing) to what I've read on the Net regarding the Danish cartoons by making you aware that other comic book and cartoons published in France during the last 20 years have similarly made fun of sacred Judeo-Christian symbols.
The publication of these works have generated many complaints and even legal actions, but the legal systems have coped with the issues raised in a civilized manner.
When you look at the other works mentioned below, you will hopefully realize that cartoonists have been equal opportunity offenders - I dare say that the Muslims have been treated with kids' gloves compared to others.
A word of warning: the links below fold lead to very graphic, shocking images. They are not suitable for workplace. If you are easily offended, do not proceed.
I'm going to approach this in chronological order.
1) In 1973, cartoonist Marcel Gotlib wrote and drew a story entitled GOD'S CLUB for the satirical adults-only magazine L'ECHO DES SAVANES. Gotlib is jewish and his family died in the camps.
In the story, Jupiter, Wotan, Jehovah. Allah and Jesus have a party, boozing, telling dirty jokes, watching stag films, masturbating, etc.
Link to Page 5 of the story
Link to Page 6 of the story
The story geberated a lot of complaints from offended Catholics, but no legal action. It was later collected in Gotlib's "RHAA LOVELY" series (Vol. 2) and is still in print today.
2) Our second case has proved more inflammatory. In the early 1980s comics writer JM Gourio and artist Philippe Vuillemin serialized a series of holocaust-themed cartoons and stories in the satirical adult-only magazine HARA-KIRI, collected under the title "HITLER = SS" (a joke on the 1968 "CRS = SS" rallying cry).
The stories were then collected into a book that immediately became the subject of numerous lawsuits from Jewish organizations and Holocaust survivors. It was banned in some countries, not in others.
You can download the book here. (that's the page from which you download, not the actual pdf doc)
Here's a link to the commentary in English on the decision by the Spanish Constitutional Court forbidding its publication (read from p.41) (pdf)
For more details, I recommend the French Wikipedia entry on the book.
Despite its clearly offensive contents, HITLER=SS is still available today.
3) In 1986, writer/artist Maester has embarked on a popular series of stories featuring the cartoony Sister Marie-Therese des Batignolles, a nun who drinks, curses, masturbates for Jesus, etc. These are published in the magazine FLUIDE GLACIAL, created by Gotlib, and have been collected into 5 books so far.
Here is a link to some FLUIDE GLACIAL covers featuring Soeur Marie-Therese.
The series has been the object of much complaining from Catholics, including one lawsuit, dismissed on parody grounds.
I hope these three example have helped place the long tradition of European cartoon iconoclasm in a better context.