Fourmilab Switzerland
John Walker: 2 Thessalonians
The actual Biblical text of 2 Thessalonians taken from the King James Version of the Bible.
Other
Ray Stedman: Adventuring Through the Bible
"Adventuring Through the Bible" is a comprehensive guide to the entire Bible with Bible commentary. This site is an excellent place to start if you are new to the Bible and/or have questions about evangelical Christianity.
Bible.org
2 Thessalonians: Introduction, Argument, Outline
A long and detailed introduction to 2 Thessalonians that includes the major themes, characters, and significance of the message in the book.