From the NSDA Events page:
"Speech involves a presentation by one or two students that is judged against a similar type of presentation by others in a round of competition. There are two general categories of speech events, public address events and interpretive events. Public address events feature a speech written by the student, either in advance or with limited prep, that can answer a question, share a belief, persuade an audience, or educate the listener on a variety of topics. Interpretation events center upon a student selecting and performing published material and appeal to many who enjoy acting and theatre."
Official rules for all Speech events (from the NSDA's Unified Manual, pp. 45-56, 58-60)
Speech events in the NSDA's Competition Events Guide (pp. 1-63)
Interpretation Resources -- overall Interp Guide (NSDA), guide to teaching Interp (NSDA)
Dramatic Interpretation (DI) -- What to Expect Competing in DI (NSDA), Intro to Coaching DI & HI (NSDA)
Duo Interpretation (DUO) -- What to Expect Competing in DUO (NSDA), Performance Breakdown: Crafting a Duo (NSDA)
Humorous Interpretation (HI) -- What to Expect Competing in HI (NSDA), Intro to Coaching DI & HI (NSDA)
Program Oral Interpretation (POI) -- What to Expect Competing in POI (NSDA), Getting Started Guide (NSDA), guide to teaching POI (NSDA)
Public Address Resources -- guide to teaching Public Address (NSDA)
Extemporaneous Speaking (USX, IX, MX) -- Extemp Textbook (NSDA), Top 5 Extemp Tips (NSDA), What to Expect Competing in USX (NSDA)
Informative Speaking (INF) -- What to Expect Competing in INF (NSDA), Creating a Solid Foundation (NSDA), INF Speech Breakdown (NSDA)
Original Oratory (OO) -- What to Expect Competing in OO (NSDA), OO Textbook (NSDA), Research in OO: Source Evaluation (NSDA)
Supplemental Resources -- Supplemental and Consolation Events Guide (NSDA)
Declamation (DEC) -- DEC Starter Kit (NSDA)
Expository (EXP) -- EXP overview (Eastside S&D)
Extemporaneous Commentary (EXC) -- EXC Starter Kit (NSDA)
Impromptu (IMP) -- IMP Starter Kit (NSDA)
Original Spoken Word Poetry (SW) -- Getting Started with SW (NSDA)
Poetry (POE) -- POE Starter Kit (NSDA)
Pro Con Challenge (PCC) -- How to Compete in PCC (NSDA)
Prose (PRO) -- PRO Starter Kit (NSDA)
Storytelling (STO) -- STO Starter Kit (NSDA)