Mosaic engineering have released VAF-TXi anti-aliasing / anti-moiré filter for Canon T2i (550D), T3i (600D), & T4i (650D). Designed to cut down aliasing, moire and false detail, resulting in a much better picture.
http://store.mosaicengineering.com/VAF-TXi-Moire-Aliasing-Filter_p_14.html
you can see Andrew's example of the version for 5D here:http://www.eoshd.com/content/7120/canon-5d-mark-ii-mosaic-engineering-vaf-5d2-anti-aliasing-filter-review
I have mine on the way, I'll let y'all know how it works ;)
JG