I love to do yoga. Before and between my babies, it's all I ever had to do to maintain my weight. It can keep you fit in ways you never imagined, and it makes you feel good....helps me keep the aches and pains at bay. It's also known to increase metabolism, help regulate blood sugar levels, improve breathing and posture, and lower blood pressure and stress levels. You can buy a good dvd for around ten dollars, so it's not a big deal if you get tired of the routine eventually and want to buy a different one. I actually prefer to do my yoga at home, even though my gym offers regular classes. I hate to contort myself and have my butt in the air doing downward dog in a room full of people with mirrors all around

. It's just not as relaxing to me that way.
I also like my pilates ball. I haven't gotten that much into Pilates yet, but I've gotten a bunch of other exercises for it off the net. Good for strengthening your core. Mine was about $15 at walmart, and it came on a circular stand to stabilize it when you need it-but it's got resistance bands attached to do upper body work, too.
Yeah-you should always weigh in the morning, after bathroom and before eating. And always with the same type (i.e. robe) of clothes or none. THat way there are as few variations as possible.
On top of all the food and drink during the day, everyone retains more
water in the evening. A have a friend whose a jeweler, and she tells me to always try on jewelry I'm thinking about buying in the morning, because standing/sitting all day at work, sodium intake, etc can make you swell significantly enough to affect things like ring, anklet, and bracelet sizes.
On another forum I go too someone posted some study findings about this subject, and it was pretty interesting. They weighed a woman several times a day, every day for a month. She didn't actually gain or lose any weight-the a.m. control weight on the first and last day were the same within less than a pound. But the daily scale fluctuations were horrible. There were days when she varied as much as 8 pounds! In one day! Changing your clothes, what you've had to eat (still solid in your stomach), and what time of day you weigh all make a difference.