Create your own After Effects filter? Well actually it would be a Pixel Bender plug-in for CS4, and you can just download it from Maltaannon's Introduction to Pixel Bender tutorial page.
Apparently, you can also do Bicubic resampling with Pixel Bender, which is something that AE lacks (except with 3rd party filters). This demo version needs work to be useful in AE though.
Update: Maltaannon has a bit more on Sept 4 in Pixel Bender and aeUIControls.