If your WordPress blog is hosted at WordPress.com (like this one), you may know that source code in posts is formatted and highlighted using a shortcode, as explained here.
Until recently, R was not on the list of supported languages (neither was Perl), but I noticed today that both of them are now supported. This may have happened months ago and I just wasn’t aware of it. I spent a merry hour or so updating my old posts in the R category, so the code should now feature pretty colours. Let me know if you spot any errors that I may have introduced inadvertently.
I guess this is in some sense recognition that R is now used quite widely and that usage is growing.
What You're Doing Is Rather Desperate 
Hi there,
If you’re interested to know more about how this came about, I wrote about it some time ago here:
http://www.r-statistics.com/2010/09/r-syntax-highlighting-for-bloggers-on-wordpress-com/
Thanks Tal – so yes, some time ago and I completely missed it!
Not directly related, but wikipedia recently updated their syntax highlighting to include r code automatically after a year or so of languishing on the bug list.