There is certain wedding etiquette related to gifts that most people these days just ignore. To me, it's sad and appalling, but oh well! I guess I am a traditionalist in some aspects and I'm okay with that. I will share this traditional etiquette:
1) It's in very poor taste to print the registry info. on the wedding invitation, even though it is commonly done in more recent years. It's in less poor taste to put in on a wedding website, but traditionally, you would find out where someone was registered by asking someone close to the family (if you weren't part of the family), or it was expected that the couple would register at a department store where they live. These days, you can search registries online (Bed, Bath & Beyond, Target, Amazon, etc.) to find out if the couple is registered there. If you don't want to search out a registry, then you give money! :)
2) It's also in poor taste to directly ask for money. Period. No matter how you do this (HoneyFund, PayPal, etc.), it's tacky. You might be fine with being tacky. :)
3) The bride & groom are not sherpas. They should not be tasked with bringing their many gifts from their wedding home with them on their wedding night! Gifts should be MAILED or otherwise delivered either before or after the wedding. Usually couples have to figure out who is going to get all the gifts from their venue to wherever they will be opening them, and it's a hassle. How rude of some guests to expect the bride & groom to do this! Etiquette says to mail your gift. So if you can't mail a physical gift, the most polite thing to do is to bring something very small (in effect, a card with money in it) as your gift, or better yet, MAIL that card with money in it!
I second the recommendation to create a small wedding registry of only items the couple would be happy to have, perhaps on Amazon where many types of items can be had, and this makes it easier for guests to have items delivered (keep in mind the image of bride & groom as sherpas!). Many guests will likely give cash/checks, or more personal gifts (like my godmother who gave us a handmade quilt), as they see fit.