A movie or a cheap restaurant can make for a good "cheap date." You could also rent a movie and watch it at home together. There is many cheap places, but it also depends on what you consider to be "cheap."
Going to the beach, hiking, playing a sport, etc.
You could take her to a strip club. Drink lots and then go home and nail her
Pinterest has some awesome and cheap ideas for craft ideas for kids to make on a rainy or sunny day! Also Parent 24 has some really cheap ideas for crafts for kids to do themselves.
There are a lot of websites out there that can offer you cheap but fun date ideas. Here is what i think the best webiste for the information you are looking for. http://www.niftydateideas.com/
Dinner can be cheap if you use coupons when going out. You could always do a dinner date staying in as well, and take turns cooking for each other and having a candle light dinner.
There are a number of different websites that offer cheap meal ideas. You can find some cheap meal ideas at All You, Quick And Easy Dinner, and WebMD.
The Delish website offers some fantastic cheap dinner ideas. You could also try the Eatingwell and the Greatist websites for some further suggestions.
Some cheap and fun ideas for a housewarming gift would be something you make on your own. Maybe consider making a vase or a card.
There are a lot of ways one can have a cheap date like going to the movies, go shopping, watch a movie at home, take a drive to a park or lake, it's up to one.
Some cheap dinner ideas for students are going to the cafeteria of your college/school. They will often offer cheap meals. You could also try to eat food that is not to expensive such as rice or spaghetti with a couple of eggs with some lettuce and olive oil.
We would like to update our home. What are some cheap home design ideas for the master bedroom?
You can find many wonderful ideas for cheap senior travel at www.seniortravel.about.com and www.seniorliving.about.com. Look into group tours organized for those in their senior years.