Aerogrammes
Airmail stamps
APO
Back-cover cancellations
Balloon mail
Based on color, eg collect only red stamps
Based on number of Perforations
Based on shape, eg triangles
Bilingual, eg Canadian
Blimp / Zeppelin mail
Booklets
Bus Post Office
By category of person, eg presidents or
    inventors
By date, eg during certain wars, such as WW 2
    or Civil War
By geographic area, eg South America
Cancel-To-Order (CTO) - just cancelled but not
     mailed
Cancels from abandoned POs
Catapult mail
Censored Mail
Cinderellas
Circular Cancels
Coils
Colored Cancellation
Commemorative stamps – stamps to                      commemorate events, anniversaries, etc.
Condition - Avg to Superb
Condition - mint, never hinged, used, no gum
Covers
Covers marked with Damaged stamp
Covers with Caches
Covers with advertising cache
Covers with embedded postage
Damaged mail
Definitive stamps
Denominations
Different colors of same denomination
Encoded (need a decoder to read hidden msg)
Errors, eg picture at an angle to the stamp, Freaks, Oddities
Essays
Event Covers
Fancy cancels - special, usually made from cork
Final Run - Bus PO
First day covers
First Flight Covers
First Stamps of an issue
Flag Cancellations
Foreign, eg British Commonwealth, one
     particular country, countries gone
Fractional amounts - eg, 1/2, 3/8 cents
Hand-cancelled
Imperfect Between - on a sheet
Imperforates
Inverts
Joint issue - same stamp issued by two or more
     countries
Killer cancellations
Limited Issue
Line Pairs
Metered
Miniature Sheets
Miniature stamps
No longer existing countries
Non-denomination stamp
No-perf edge stamp
Numbers on plate block, booklet, or coil, or
     marginal markings
Numeral Cancels, ie, an oval cancellation with a number inside
Occupation - usually overprints
Official
Overprints
Parachute mail
Parcel Post
Pen Cancels
Penalty using official for private use
Perfins
Post Cards
Postage due, Special Delivery, Priority,  back of
     the book
Postal Markings
Postal Stationery
Poster Stamps
Pre-cancel dated
Pre-cancels - local and national
Private Issue
Proofs
Provisional Stamps
Railroad cancels
Railroad Post Office
Reply pre-paid cards
Revenue stamps – stamps issued to pay taxes;
    state & federal
Roulette-edged
Rocket mail
Same stamp- Different colors
Same stamp but looks microscopically different
Savings stamp
Se tenant - describe attached stamps that are
     different from one another
Semi-postal
Sheets
Ship canceled
Singles vs Pairs or Other Multiples
Socked on the Nose
Special Cancels - to commemorate a local
    event, person, etc
Specimen - overprint
Stamp-less cancelled cover
Stamp on stamp
Surcharge - overprint to increase stamps value
Telegraph stamp
tete beche - two stamps head to tail
Topical stamp collecting – many
Vertical Pairs, Trips, Quads
War tax stamp
Wreck cover
Collecting Categories
Philately is more than just collecting "regular" postage stamps.  As you can see from the list below, there is a huge variety of stamps and covers (envelopes) that one can collect.  Many collectors combine stamp/cover collecting with historical events, such as wars, creation of new countries, and celebrating the anniversaries of states/territories.
Welcome to the Garden City Stamp Club
                 of Missoula, Montana