I have a website that is a cash gift registry service. A lot of people use us for honeymoon registries. It's actually quite hard to build a site like this from scratch, but if you wanted to point your couples in the direction of of site, we would be happy to be a resource to you: http://www.depositagift.com
I went to your site and see that you are also connected to the Green Bride Guide. So are we :)
Feel free to email me if you'd like to connect about this.
I also found the wish registry to be fantastic- we have both a honeymoon and household stuff that translate to a cash registry, we have all kinds of things added to it- it has been fantastic for us! we are using www.uponourstar.com - Hope That Helps!
