Make a cash gift to an environmental group.
All these groups -- and there are thousands -- will happily take money via cash, check or credit card. Some even offer estate plan help so that you can leave a final bequest to the group.
Your gift obviously will help the environmental group continue its efforts. But it also could save you some tax dollars. If you itemize, you can deduct your donations to IRS-approved charities. Just make sure you get a receipt in case the IRS has follow-up questions. If your gift is one of your final ones, it also could help lower any potential taxes on your estate. See your attorney or financial planner on how to structure these types of estate gifts to you maximum tax benefit.