Below you will find the castings for the first movie. Thank you UKHP (which has been closed for some time) for this source of information which I have edited to fit the site.

Students, Trio and Arch Enemies. Harry Potter: Daniel Radcliffe (mwee! He *writes*! ahem...)
Ron Weasley: Rupert Grint
Hermione Granger: Emma Watson
Draco Malfoy: Tom Felton
Vincent Crabbe: Jamie Waylett
Gregory Goyle: Joshua Herdman
Virginia 'Ginny' Weasley: Bonnie Wright
Fred Weasley: James Phelps
George Weasley: Oliver Phelps
Percy Weasley: Chris Rankin
Neville Longbottom: Matthew Lewis
Oliver Wood: Sean Biggerstaff
Dean Thomas: Alfie Enoch
Pansy Parkinson: Katharine Nicholson
Terence Higgs: Will Theakston
Alicia Spinnet: Leila Sutherland
Katie Bell: Emily Dale
Angelina Johnson: Danielle Tabor
Lavender Brown: Kathleen Cauley
Adrian Pucey: Scott Fearn
Lee Jordan: Luke Youngblood
Millicent Bulstrode: Helen Stuart
Penelope Clearwater: Gemma Padley
Slytherin Keeper 'Bletchley'
Justin Finch-Fletchley: Edward Randell
Seamus Finnigan: Devon Murray (I don't appreciate incinuation, Longbottom!)
Colin Creevey: Hugh Mitchel

teachers

Albus Dumbledore: Richard Harris
Minerva McGonagall: Maggie Smith
Rubeus Hagrid: Robbie Coltrane
Severus Snape: Alan Rickman
Gilderoy Lockheart: Kenneth Branagh
Professor Quirrell: Ian Hart
Madam Hooch: Zoe Wanamaker
Filius Flitwick: Warwick Davis
Argus Filch: David Bradley
Madame Pomfrey: Gemma Jones
Irma Pince: Sally Mortemore
Professor Sprout: Miriam Margoyles

Family, Shopkeepers and Previous Headmasters.

James Potter:Adrian Rawlings
Lily Potter: Geraldine Somerville (I know a school called that 0_o)
Vernon Dursley: Richard Griffiths
Petunia Dursley: Fiona Shaw (I am insulted)
Dudley Dursley: Harry Melling
Molly Weasley: Julie Walters
Arthur Weasley: Mark Williams
Tom Riddle: Christian Coulson
Lucius Malfoy: Jason Isaacs
Mr. Ollivander: John Hurt
Mr. Borgin: Edward Tudor-Pole
Armando Dippet: Alfred Burke

Ghosts, Talking Objects, Animals and Other Arch Enemy. Moaning Myrtle: Shirley Henderson
Nearly Headless Nick: John Cleese
Fat Friar: Simon Fisher-Becker (I love that show...)
Grey Lady: Nina Young
Bloody Baron: Terence Bayler (and he looks too jolly, too! argh...)
The Fat Lady: Elizabeth Spriggs
Peeves: Rik Mayall
Sorting Hat Voice: Leslie Phillips
Aragog Voice: Julian Glover
Voldemort: Richard Bremmer
Hedwig: Ook the Owl