The short answer is "yes".
There are three DANTES-sponsored programs that provide dozens of tests on dozens of subjects that you can take to earn college credit: the College Level Examination Program (CLEP), the DANTES Subject Standardized Examination (DSST) program, and the Excelsior College Examination (ECE) program. Tests from any of these programs are free.
There are also other test-for-credit programs, such as the Thomas Edison State College Examination program (TECEP).
However, not all institutions of higher learning will count credit from these tests toward degrees they award or will give you full credit for these tests. You should make sure the school you want to get a degree from will both count the tests you want to take and will give you full credit for them. In addition, many colleges allow you to take a course's final exam or totally separate tests instead of taking a course that count toward degrees they offer.
None of these tests is easy, and you shouldn't expect to be able to take any of them without studying (sometimes a lot) beforehand. They are all the equivalent of a college final exam – in the case of the CLEP tests, the final exam for two-semester college course.
DANTES Test Control Officers (TCOs) are authorized to administer DSSTs, ECEs, and some CLEP tests in addition to other tests like SATs, ACTs, and others. Not all ESOs are TCOs, however. Check with your ESO to see if s/he can administer these tests and if s/he can administer the specific test(s) you want to take. CLEP tests the TCO can't administer are offered at national test centers.
It depends. Most Coast Guard TCOs don't have these tests on-hand and must must order them as needed. Delivery time can take up to two weeks.
However, some TCOs are have what DANTES calls "stocking units", meaning they keep an inventory of tests on-hand all the time.
Check with your ESO to find out if s/he is a TCO, if your unit is a stocking unit, and (if so) if your TCO has the test you'd like to take in his/her inventory.
Official study guides for most DANTES-sponsored tests (DSSTs and ECEs) are available via other pages on this web site. Official study guides for CLEP tests are available from Navy Knowledge Online. Once you've logged in, click on the "Learning" tab, and scroll down to the windows labeled "Official CLEP Study Guides Part 1" and "Official CLEP Study Guides Part 2".
Other study materials for some of these tests may be available from your ESO.
For more information, go to the Study Materials page of this web site.