…more formally called RAS syndrome "Redundant Acronym Syndrome syndrome"

PIN Number "Personal Identification Number number"
similarly the ISBN number "International Standard Book Number number"
& VIN number "Vehicle Identification Number number"
LCD display "Liquid Crystal Display display" (but not LED display for those ancient enough to remember "Light Emitting Diode display")
VOIP protocol "Voice Over Internet Protocol protocol"
ATM machine "Automated Teller Machine machine"
RAM memory & ROM memory "Random Access & Read Only Mememory memory, respectively"
UPC code "Universal Product Code code"
HIV virus "Human Immuno Virus virus"
SAT test "Scholastic Aptitude Test test"
similarly the LSAT test "Law School Admission Test test" but, formally, not the ACT test… American College Testing was originally the name of the firm
PDL language "Page Desctiption Language language"
PDF format "Portable Document Format format"
COBOL language "COmmon Business Oriented Language language"
SAM missile "Surface to Air Missile missile"
similarly ABM missile "Anti-Balistic Missile missle"
ALCOA company "ALuminun COmpany of America company"
VAT tax "Value Added Tax tax"
CD Disc "Compact Disc disc"
RPN notation "Reverse Polish Notation notation"
MIDI interface "Musical Instrument Digital Interface interface"
DAT tape "Digital Audio Tape tape"
MASH hospital "Mobile Army Surgical Hospital hospital"
IRA account "Individual Retirement Account account"


and for the rest of the fogies (all two of y'all :P ) DC comcs "Detective Comics comics"

Feel free to add other examples, but please 'white-out' the explanations.
Note that bilingual examples eg "Please RSVP" are not included.