The categories I collect are definitely idiosyncratic, especially since I've (very slowly) been trying to reduce the categories I collect in recent years. Highlights below, followed by some wantlists! (More wantlists are available as well.)
My favorite category of skeds - the older the better. The categories I collect here are pretty specific, as these skeds can be expensive. I'm especially active in seeking college football for about 2 dozen specific teams, with a few in my collection dating back into the late 1800s.
I also collect all vintage college hockey and rowing, all skeds from Princeton and Amherst, and vintage stuff in a few other categories.
Red Sox, Bruins, Celtics, Dodgers, Packers
Lots of categories here. I collect almost everything in these favorite college sports or categories:
Football (Division I and Division III)
Ice hockey (men's and women's)
Rowing (men's and women's)
Lacrosse (Division I men's and women's)
Basketball (men's, Division I and Division III)
NESCAC schools
I also collect many other college sports, but usually only for specific schools (for example, I collect wrestling schedules for about 8 specific teams and men's and women's soccer for about 30 teams). Can send more details if anyone's actually interested. :)
Okay, this is where it gets really idiosyncratic. I collect most pocket skeds in the following categories: Red Sox, Bruins, Celtics, Patriots, Dodgers, Packers, AFL football (1960-69), WHA hockey, Red Sox farm teams, European hockey, international rugby, Yomiuri Giants baseball, some English/Scottish soccer, women's pro soccer, Cape Cod League baseball, plus a few other categories.
But I don't collect other pro sports teams that are not listed above.
Red Sox 1954 1953 1952 1950 1948 1946 1945 1944 1943 1940 many 1937 and earlier
Bruins 72-73 68-69 67-68 65-66 many 63-64 and earlier
Celtics 73-74 68-69 67-68 many 63-64 and earlier
Patriots 1966
Whalers need all 74-75 and earlier
Alabama: 1973, 1972, 1971, 1970, 1969, 1968, 1966, most 1964 and earlier
Amherst College : ALL EXCEPT 2003, 2004
Army: Many 1973 and earlier
Boston College: 1972, 1971 (nice cond), 1970, 1969, 1967, 1965, 1964, 1962, most 1960 & earlier
California: 2012 (cannon), 1971, 1962, 1961, 1960, 1959, 1958, many 1950 and earlier
Cornell: 1978, 1977, many 1974 and earlier
Dartmouth: 1977, 1972, 1969, 1968, many 1964 and earlier
Harvard: 1981, 1979 (not radio station), 1978, 1977, many 1975 and earlier
Holy Cross: 1977, 1972, 1971, 1968, 1966, many 1964 and earlier
Iowa: 1969, 1968, 1967, 1965, 1959, 1955, most 1953 and earlier
Michigan: Many 1962 and earlier
Minnesota: 1977 (photo), 1970, 1969, 1968, 1966, 1965, 1961 to 1964 (pockets), most 1960 and earlier
Navy: 1972, 1970, 1968, 1966, 1963 (photo), 1961, many 1958 and earlier
Notre Dame: 2013 (#51 with teammates), 1964, 1962, many 1959 and earlier
Princeton: 1982, 1980, 1979, 1977, many 1973 and earlier
Southern Cal: 1975 (photo), 1964, many 1958 and earlier
Stanford: 1967, 1966, 1965, 1963, 1962, 1960, 1959, 1958, 1957, 1954, most 1947 and earlier
Texas: 1976 (Rooster Andrews), 1969, 1962, most 1960 and earlier
Virginia: 1976, most 1973 and earlier
Washington: 1976 (photo), 1974 (photo), 1973, 1972, 1971 (photo), 1970, 1968, most 1963 and earlier
Williams College: ALL EXCEPT 1989, 2000, 2001, 2003, 2004, 2012, 2014, 2015
Wisconsin: 1969, 1968, 1964, most 1962 and earlier
Yale: 1969, 1966, 1962, 1961, many 1958 and earlier
Boston College (BC): 78-79, 77-78 (except Riley and Augustine), most 74-75 and earlier
Boston University (BU): Most 77-78 and earlier
Cornell: 81-82, most 78-79 and earlier
Dartmouth: 90-91 (hockey-only), 81-82, 77-78, 76-77, 74-75 (hockey-only), most 73-74 and earlier
Harvard: 78-79, most 76-77 and earlier
Maine: 83-84 (hockey-only), 82-83, 81-82, 80-81, 79-80, 78-79 (hockey-only), most 76-77 and earlier
Michigan: Most 70-71 and earlier
Michigan St: 79-80, 78-79, 74-75, most 72-73 and earlier
Minnesota: 82-83 (color photo), 74-75, most 70-71 and earlier
New Hampshire: 79-80, 78-79, 77-78, most 75-76 and earlier
North Dakota: 96-97 (hockey-only), 81-82, 78-79, most 76-77 and earlier
Northeastern: 79-80, 78-79, most 75-76 and earlier
Notre Dame: 74-75, 73-74, 7273, 7071, most 68-69 and earlier
Princeton: 80-81, 78-79, 77-78, 76-77, most 74-75 and earlier
Princeton (women's): most hockey-only 96-97 and earlier (except 94-95, 89-90, 88-89)
Vermont: 79-80, 78-79 (hockey-only), most 77-78 and earlier
Wisconsin: 78-79, most 72-73 and earlier
Yale: 87-88 (hockey-only), most 79-80 and earlier
Looking for any schedules that include men's or women's crew for the teams/years below. For this sport only, I also collect multi-sport combos like "spring sports" or oversized schedules like postcards (in addition to traditional pocket-sized schedules).
Boston University: I NEED ALL EXCEPT 09, 08, 07, 05, 04, 03, 02, 01, 00, 99
California: (NEED ALL 03 to now); also need 00, 98, 94, 91, 86, 84, 83, 82, 80, 78, 76, 75, most 73/earlier
Cornell: 19, 18, 06, most 03 and earlier (except 84, 87, 94)
Dartmouth: 19, 08, 06, 05, 01, 00, 98, 97, 95, 92, 91, 90, 86, most 84 and earlier
Harvard: 94, 93, 92, 91, 90, 89, 88, 87, most 85 and earlier
Michigan: 19, 18, 13, 10, 08, 07, 05, 01, most 99 and earlier
Navy: ALL EXCEPT 02, 01 (only have lightweight crew for 01), 80
Northeastern: 19, 18, 17, 16, 15, 14, 00, 97, 94, 93, 91, 89, most 85 and earlier
Princeton: ALL EXCEPT 08, 04, 03, 96, 65, 64, 89, 88, 87, 86, 84
Stanford: 19, 18, 17, 16, 15, 14, 10, 00, 98, most 95 and earlier (EXCEPT 87, 91)
UCLA: 19, 18, 17, most 04 and earlier
Washington: ALL EXCEPT 09, 08, 07, 06, 05, 04, 03, 01, 00, 97, 95, 94, 91, 89, 88, 87, 79
Wisconsin: ALL EXCEPT 89, 84
Yale: 19, 18, 17, 16, 07, 98, most 95 and earlier
Need 1928, 1922, 1913, 1912, 1911, 1900, 1898, 1893 and earlier
(also need some ticket color variations for years I already have)
Need 1919, 1914, 1913, 1912, 1911, 1889 and earlier
(also need some ticket color variations for years I already have)
Need 1939, 1922 and earlier
Need ALL EXCEPT 1964, 1941, 1939, 1938
Need almost all pre-1930 Princeton hockey
Need many pre-1930 Princeton baseball vs Harvard or Yale only
Need many pre-1931 Notre Dame football (Knute Rockne era and earlier)
Need almost all pre-1920 Army football
Need almost all 1923-1925 Illinois football (Red Grange!)
Plus some other random stuff. :)