I'm a bit OCD, so I regularly check my (admittedly underwhelming) Blogger stats, and one thing that has jumped out at me is that I have been regularly getting visitors from a Google search for "why no 4e ritual cards" query. I think most of these clicks wind up at my post on "D&D the CCG: Ritual Cards", but I'm not entirely sure that post has been helpful for those people finding it from the Google search, but seeing as the post was from mid-February and still is in my regular weekly top-5 for page views, I think this topic should be revisited.
I think Wizards of the Coast is missing out on a great supplemental product by not selling cards for their Rituals. Of course, from what I've gathered around the forums, rituals don't see a whole lot of use in a lot of 4e games, which I think is sad, but is probably a by-product of the general delve-format that WotC has been pushing since 4e's release.
These would be perfect as a treasure handout when the party finds a ritual scroll, as well as being a great way for a wizard to organize his spellbook without a lot of hand-cramping writing and character sheet clogging to deal with.
Now, I'm not really willing to put in the time and effort to create Ritual Cards for the entirety of the D&D 4e ritual library. I'm also reluctant to trod upon WotC's copyrights by putting all that stuff up on the interwebs for just anyone to take. However, if anyone does want some custom-made ritual cards, I would be happy to make them for you (for personal use, of course). I would insist that one have either a DDI subscription (so mine isn't being leeched upon) or at the very least, copies of the books from which the rituals are taken. I would also love to hear how they wind up being used in-game! Email me at sully33 at gmail dot com if you want some ritual cards for your spellcaster.