NARA will release the images of the 1940 U.S. Federal Census on April 2nd. FamilySearch and others are sponsoring a project to index the images. The resulting indexed census will be available for free at FamilySearch and elsewhere.
You download a program that runs on your computer (either PC or Mac). It’s the same one some of us have used for other FamilyHistory indexing. Then, when the project starts, you download an image. I’m guessing that for the 1940 Census the image will be one page, with 40 entries. You transcribe the names and some other data for the people on the page, and upload the batch when you’re done. You can return a batch if you find it difficult, and each page is indexed twice and compared so you don’t have to worry about yours being letter-perfect. You get to select a batch to index; if you’re lucky you might run across yourself or an ancestor in the process. It’s an easy way to give back to the genealogical community.