In reply to mypyrex:
My personal experience of dealing with funerals and that of family and friends who have done so is that the charity is usually one the deceased supported.
Even if I couldn't get totally on board with a charity it is more constructive than the old practice of spending at a florist who you don't know and in turn may spend their disposable income in a way in which you don't approve. (It probably makes me a bad person that I am chuckling to myself imagining the old dear in the local florist dressed up in neo nazi regalia). The way I see it, a donation is giving by proxy one last time for the person who has passed.
If it was something I absolutely disagreed with I'd quietly donate to something else. I had a situation once in the US where they were asking for donations for a charity that was prolife and in particular anti stem cell research. I knew these were nothing along the lines of the sympathies of the person whose funeral it was. Despite being an ungodly atheist I instead donated to a christian charity that educated and campaigned in favour of stem cell research and promoted discussion of it in christian circles.