This one is a no brainer. For $20 worth of weather stripping you can save a bundle on you heating bills. Try closing up the cracks and gaps around your windows and doors. You will be amazed at what a difference it will make when the cold weather arrives. All sorts of drafts and air leaks can be beaten this way. You don't need to be much of a handyman to use this stuff either. Most of it is peel and stick self-adhesive these days. Couldn't be simpler. If you have window or wall mounted air conditioners, invest in an insulated elastic cover. An awful lot of heat is lost through uncovered AC units in the winter.
(My most recent project. I'm the local lawyer in my synagogue. I was asked to lead the discussion on Id theft on this occasion. I had fun and a number of folks told me afterward how much they appreciated my effort.)
If you are looking for something useful to do with your spare time that won't cost you a penny, consider volunteering you services. You may be thinking, what can I do that would matter to anyone. The reality is that you can do plenty. Whether it be visiting the elderly in nursing homes or getting involved with your church or synagogue, or any number of other worthy causes, there are loads of useful activities out there waiting for someone to just step up. Plenty of us have a useful skill that could help others if shared. I have learned that it doesn't take a huge effort to make a meaningful difference to others. That it can be done for little or no financial commitment makes it that much better in my view.
Forget about going out to eat, especially socially. A home cooked meal is a fraction of the cost of a restaurant. Invest in a good cookbook and entertain at home. Not only will you save money, you might actually enjoy it more. Cooking can be fun and more healthy for you since you know exactly what you are eating.