Monday, April 18th is the last day to file Federal Income Taxes this year. If you prefer to use paper forms the Government Information & Law department at King Library still has the basic forms, though at this late date you may want to file electronically.
If you are interested in just where your Federal tax dollars go you should take a look at the White Houses' 2010 Tax Receipt page. By entering your 2010 information you can get a break down of how your Federal tax dollars were spent.
If you'd like to know more about tax law then you should visit the library.
The Internal Revenue Code of the United States is spelled out in Title 26 of the United States Code (being the general and permanent laws of the United States). The IRC has seen plenty of revision over the last 80 years. If you are interested in the history of tax law reform over the course of the 20th century the Miami University Libraries have publications of the major revisions of the tax code. The library also has the current edition of the United States Code if you would like to take a look at the current tax laws (the current edition being published in 2006). If you would prefer to look up the USC in electronic format it is available in a verified version from the Government Printing Office on FDsys.gov
The USC is the official codification of the laws of the United States and is compiled every six years from laws passed in each session of Congress, called Slip Laws (referring to how they are printed). Slip Laws are compiled after each session of Congress into the US Statutes at Large (MU Libraries / FDsys.gov), and every six years these laws are entered into the new edition of the USC. While Slip Laws are just as legal as any passed law, it is still good practice to check the USC if the law you are looking for has been compiled.
The USC is the law, but it isn't the absolute final word in how laws are enforced. The Code of Federal Regulations (MU Libraries / FDsys.gov) contains the regulations passed by the Federal Executive Agencies which are broadly responsibly for determining how the laws in the USC will be enforced.
Both the USC and the CFR are organized into 50 titles each of which correspond to each other (title 26 of the USC is the Internal Revenue Code with title 26 of the CRF being the regulations stemming from those laws). If you are researching taxes, you'll want to check both the laws and regulations.