Below is a complete list of the delegates to the Synod of Dort. The list is pulled from two different sources, so the spelling is not consistent (Some names are Latinized, others Anglicized).
There were no official delegates from several regions. The Dutch states of Holland and West Freisland were excluded. They had attempted to send Simon Episcopius as their delegate, and one of the first acts of the synod was to revoke his status. In France, Louis XIII opposed the synod and prohibited French participation. In Brandenburg (Germany), the Lutherans prohibited representation.
Only official delegates are listed. This excludes deputies, secretaries, observers, etc.
England:
George Carleton (1559–1628)
Joseph Hall (replaced by Goad) (1574–1657)
Thomas Goad (1576–1638)
John Davenant (1576–1641)
Lancelot Andrewes (1555–1626).
Scotland:
Walter Balcanqual (1586–1645)
Samuël Ward (died in 1643)
William Ames (Guilielmus Amesius) (1576–1633).
Heidelberg (Palatine, Germany):
Abraham Scultetus (1566–1624)
Paul Tossanus (1572–1634)
Hendrik Alting (1583–1644).
Hessen (Germany):
Georg Cruciger (1575–1637)
Paul Stein (1585–1643)
Rudolph Goclenius (1547–1628)
Daniel Anglocrator (1569–1635).
Switzerland:
Johann Jakob Breitinger (1575–1645)
Wolfgang Mayer (1577–1653)
Sebastian Beck (1583–1654)
Mark Rütimeyer (1580–1647)
Hans Conrad Koch (1564–1643)
Krefeld (Germany):
Herman op den Graeff (1585-1642) [This may be incorrect, see the comment from David below. op den Graeff was a Mennonite, and attended a different conference in 1632]
Geneva:
Giovanni Diodati (1576–1649)
Theodore Trochin (1582–1657)
Bremen (Germany):
Ludwig Crocius (1586–1653)
Matthiuas Martinius (1572–1630)
Heinrich Isselburg (1577–1628)
Wetterau (Germany):
Johann Heinrich Alsted (1588–1638)
John Bisterfeld (died in 1619)
Georg Fabricius.
Emden (Germany):
Ritzius Lucas Grimersheim (1568–1631)
Daniël Bernard Eilshemius (1555–1622).
Dutch Theologians (at large)
Johannes Polyander, (1568-1646)
Sibrandus Lubbertus, Professor, Friesland
Franciscus Gomarus, (1563-1641)
Antonius Tysius, Professor, Gelderland
Antonius Walaeus, Professor, Middelburg
Gelderland-Zutphen (The Netherlands)
Gulielmus Stephani, Pastor, Arnhelm
Ellardus a Mehen, Pastor, Harderwick
Johannes Bouillet, Minister, Warnesfield
Jacobus Verheyden, Elder, School Rector, Numeghen
South Holland (The Netherlands)
Balthasar Lydius, Pastor, Dort
Henricus Arnoldi, Preacher, Delf
Gisbertus Voetius, Pastor, Huysden.
Arnoldus Musius, Elder, Dort
Johannes Latius, Elder, Leiden
North Holland (The Netherlands)
Iacobus Triglandius, Minister, Amsterdam
Abrahamus à Dooreslaer, Minister, Enchusen
Samuel Bartholdus, Pastor, Monichodam
Theodorus Heyngius, Elder, Amsterdam
Dominicus ab Heemskerck, Elder, Amsterdam
Zeeland (The Netherlands)
Godefridus Udemannus, Pastor, Zurick-zee
Cornelius Regius, Pastor, Tergoose
Lambertus de Rycke, Pastor, Bergen up Zoon
Josias Vosbergius, Elder, Middleburg
Adrianus Hofferus, Elder, Zurick-zee
Utrecht (The Netherlands)
Johannes Dibbezius, Minister, Utrecht
Arnoldus Oortcampius, Pastor, Amersfoort
Friesland (The Netherlands)
Florentius Johannis, Church member, Snek
Philippus Danielis Eilshemius, Pastor, Harling
Kempo Harinxma à Donia, Elder, Leuerdin
Tacitus ab Aysma, Elder, Buirgirt
Overijssel (The Netherlands)
Casparus Sibelius, Pastor, Deventer
Hermannus Wiferding, Minister, Swoll
Hieronymus Vogelius, Pastor, Hasselt
Iohannes Langius, Preacher, Woolenhoof.
Wilhelmus à Broickhuysenten Doerne, Elder’s deputy
Johannes à Lauwick, Elder’s deputy
Groningen (The Netherlands)
Cornelius Hillenius, church member, Groningen
Georgius Placius, Pastor, Apingdam
Wolfgangus Agricola, Minister, Bedam
Wigboldus Homerus, Minister, Midwold
Egbertus Halbes, Elder, Groningen
Ioannes Rufelaert, Elder, Stedum
Drenthe (The Netherlands)
Themo ab Asscheberg, Pastor, Meppelen
Patroclus Romelingius, Pastor, Rhuine
Wallon (The Netherlands)
Daniel Colonius, Minister and regent, Leyden
Joannes Crucius, Minister, Harleim
Joannes Doucher, Minister, Vluisshing.
Jeremias de Pours, Minister, Wallon
Everardus Beckerus, Elder, Wallon
Petrus Pontanus, Elder of the Church in Amsterdam
Sources used:
Dutch Delegates: English Translation of the Synod of Dort, 1619
Foreign Delegates: Answers.com
Wesleyan Arminian 
How brave of these men to let their names be printed in the official Remonstrance. I wonder what became of them after the conclusion of Dort? I wonder how many of them suffered under Calvinists?
Are you being sarcastic? These are the Calvinists from Dort, so most of them were not too brave. :)
Man, these guys were all Calvinist? Did Arminians get any delegates in?
Believe it or not, Herman Op Den Graeff are a direct descendants of famous people such as:
Charles Hatfield Schulze (hero and attorney)
Andy Samuel Griffith (actor)
Amelia Lynn Shambaugh (crime victim)
Matthew Gregory Gwaltney (crime victim)
Ronald Vernon Cassill (novelist)
Charles Sherrod Hatfield (Associate Judge)
George Armstrong Custer (General)
General George Armstrong Custer is a direct descendant of Herman Op Den Graeff!
Cool!
So does the ten year old mother Sally DeWees, Richard Spohn Brokaw, and believe it or not, Richard Clair “Dick Clair” Jones! They are direct descendants of Herman Op Den Graeff!
So does Ray Leon Triplett, Henry Harley Arnold, Sering Dunham Wilson, and last but not least, Esther Jean Williams! They are direct descendants of Herman Op Den Graeff!
Best of two heroes are direct descendants of Herman Op Den Graeff:
Steven P. Zernhelt and Michael Gene Cassell!
There are other direct descendants of Herman Op Den Graeff:
Wesley K. Clark
John Waters
Ricky Borts
Believe or not, a direct descendant of Herman Op Den Graeff:
Will Geer, a star of the Waltons!
Krefeld (Germany):
Herman op den Graeff (1585-1642) was actually a Mennonite. Wiki–or whatever the original source was–is incorrect. Wiki even has him listed as a Mennonite. Apparently there was a later Mennonite Conference at Dort which was produced its own statement, to which op den Graeff signed, along with one other Krefeld Mennonite.
Looks like you’re right, nice find!
I added a note.