Not just for weddings! Check out the butterfly pyramid, the gemstone collection, and all the graphic dioramas! Also, the paleontology hall is the best; if we'd been able to afford it, we would've definitely held the wedding there.
MFAH has a lot of Impressionist art, and a color-changing light tunnel between its two buildings that's definitely worth a walk-through. They also get fabulous touring exhibits. Don't forget to cruise through the sculpture garden next door. Sometimes there are also food trucks parked nearby!
This place is cool but the main thing is it has the best gift shop ever. It's such a weirdly good gift shop that it sometimes shows up on random lists of "best museum gift shops". Admission is free, and the museum itself hosts different art exhibits so you never know what you're going to see there.
For those of you with kids, Houston has one of the best children's museums in the country. There is even stuff for tweens/young teens, and it's a fantastic place to spend a half-day or so. Be prepared to wear yourself and the kid out because there is a LOT going on in this place.
If you've never been to the Houston Zoo, or if it's been awhile, it's definitely worth visiting if the weather is good. As zoos go, it's a good one. We also considered getting married in the reptile house at the zoo, by the way.
Ever wonder what a home and garden would look like if the guy who lived there was tripping balls and had a lot of free time and apparently endless access to tiling and metalworking supplies, plus concrete? If so, the Orange Show is the place for you. It's a little further afield than the other destinations but if you want something you've never seen before, this place will not disappoint.