I have never been a fan of small wire cages, and while I have seen many people keeping rabbits just fine that way, I really wanted something more comfortable for ours. A lot of the inspiration for our build came from this lovely hutch I ran across on YouTube. We made sure to use non toxic woods since bunnies will chew! If you are building a hutch, make sure you avoid pressure treated anywhere the rabbit can reach, as well as particleboard, OSB, or MDF since that has a lot of glue. Designing and making a hutch was a great experience. I was intimidated a little at first, but this way you can make it as large as you like, and end up with a far sturdier hutch for far less than buying one from a store.
We ended up making it pretty big. With house boxes that they can climb on to be a second "loft" level. One of the things we added was a double reinforced floor. It is hardware cloth to allow messes to fall through so everyone stays clean and dry, but there's a heavier gauge fence under that to add support. The rabbits can sit on their lofts and socialize through a hardware cloth wall, or go be in their house box if they want privacy. This hutch also allows a lot of air flow. One thing to keep in mind with rabbits is that they can handle cold weather very well, but can easily overheat in the summer.
The rabbits seem to really enjoy having the space, and will often sit on their loft levels to sunbathe. Later on, I ended up a litter pan to the back of the loft levels. For some reason that's where my bunnies seem to want to toilet, so in an attempt to save the wood from getting gross, a small litter pan with some pine shavings did the trick!
Since this first double hutch, we have built an additional triple condo hutch as well.