http://libelreform.org/sign"The Libel Reform coalition brings together English PEN, Index on Censorship and our partner organisation Sense About Science to campaign to reform the libel laws of England and Wales."
A fair amount of focus on the Simon Singh case on the site, but the petition is a general one:
"Freedom to criticise and question, in strong terms and without malice, is the cornerstone of argument and debate, whether in scholarly journals, on websites, in newspapers or elsewhere. Our current libel laws inhibit debate and stifle free expression. They discourage writers from tackling important subjects and thereby deny us the right to read about them.
The law is so biased towards claimants and so hostile to writers that London has become known as the libel capital of the world. The rich and powerful bring cases to London on the flimsiest grounds (libel tourism), because they know that 90% of cases are won by claimants. Libel laws intended to protect individual reputation are being exploited to suppress fair comment and criticism.
The cost of a libel trial is often in excess of £1 million and 140 times more expensive than libel cases in mainland Europe; publishers (and individual journalists, authors, academics, performers and blog-writers) cannot risk such extortionate costs, which means that they are forced to back down, withdraw and apologise for material they believe is true, fair and important to the public.
The English PEN/Index on Censorship report has shown that there is an urgent need to amend the law to provide a stronger, wider and more accessible public interest defence. Sense About Science has shown that the threat of libel action leads to self-censorship in scientific and medical writing."
They are aiming for as many signatures as they can get before the election, so that hopefully parties will include it in their manifestos (looks like it should be in the Lib Dem one already:
http://news.bbc.co.uk/1/hi/uk_politics/8466297.stm )