Sarah Palin recently ‘tweeted’ refudiate, likely confusing refute and repudiate.
I tried to think of other examples but could only think of irregardless which has an interesting wikipedia entry.

There must be others based on mistakes that have caught on (portmanteaus like chortle - chuckle and snort - were deliberate).

(portmanteaus like chortle - chuckle and snort - were deliberate).

She says that she, in the tradition of the Bard, made the word up on purpose.  English is a living language she says.

Mark Lieberman discussed it at Language Log.

I’ll be happy if refudiate catches on and irregardless dies a swift and lonely death.

Following a link in a reader’s comment in the Guardian printless OED story today I found this predate of refudiate from 1973.
Also, from wikipedia:

The Klein bottle was first described in 1882 by the German mathematician Felix Klein. It was originally named the Kleinsche Fläche “Klein surface”; however, this was incorrectly interpreted as Kleinsche Flasche “Klein bottle,” which ultimately led to the adoption of this term in the German language as well.

An interesting claim, but as they say on Wikipedia, [citation needed].  I’ve been searching at Google Books and can find no backup for it; on page 460 of 5000 Jahre Geometrie: Geschichte, Kulturen, Menschen, for instance, it just says “die nach ihm benannte „Flasche” (auch als „Schlauch” bezeichnet)” ["the ‘bottle’ named after him, also called a ‘tube’], with no mention of this supposed distortion via English.  Until I see some proof, I’m voting for folk etymology.

Edit: I have deleted the sentence from the Wikipedia article.  It’s been unreferenced for three years, and that’s long enough.

On a slightly related note, I think hispanically was a word we definitely needed.

Some more interesting confusion I found. http://en.wikipedia.org/wiki/Shooting-brake