I'm also a fan of the tape measure, although I measure every two months. I measure myself, which is kind of hard--I like Goddess Jessica's way better.
I had my DH take a photo of me at the beginning of this journey, and he "hid" it in his computer files. I had him take another photo at 30 lbs. lost, and then I'll probably do another one at 50 lbs.--might even post the before and after then. I haven't seen either of them.
Clothes size has definitely worked for me. I've gone from a 22 to a 16 so there's a measurable difference there. The only thing to watch out for is that clothes sizes are not all equal. I can get into an Old Navy size 16, but not a Target size 16. So that can be a bit disappointing if you're not aware of it--think I'm going to shop at Old Navy from now on!
One of the ways I look at the journey is through our holiday challenges. If I can meet (or almost meet) those goals I've set for myself, it breaks the weightloss into smaller increments. Also, I made a contract with myself about a month ago where I would be perfectly on program (along with some other things) for just three weeks. That was certainly doable.
I'm on Weight Watchers and they give out gold stars for every 5 lbs. lost, which I find to be pretty motivating. They also give out bigger rewards for bigger losses. There's a woman there who has lost 218 lbs., and has probably 150 more to lose. She takes it 5 lbs. at a time, and has done really well.
Hope this gives you an idea or two!