Well, how about a wedding ring coffin?
I found this little baby at Amazon.com for $34.99 plus $5.49 shipping. It has a plaque that reads "Bury the past and move on to a new tomorrow."
There seems to be a big movement lately that divorces are something to celebrate (I wonder if Hallmark started this idea). There are divorce parties (in this particular case, it was only celebrity rumor) and divorce cakes (and stores that cater to these events). So why not bury your wedding ring?
Obviously I wouldn't advise actually burying it, unless you really need that level of closure. Especially if you rent. On second thought, with unexpected job loss and unemployment fueled foreclosures being so ubiquitous these days, I wouldn't advise burying it at all. You just might need to buy some Ramen one day. (I <3 Ramen!)
You could always leave it on your coffee table as a conversation piece. Well, unless you're dating. Because that conversation would be AWKWARD.