Mumonkan

A collection of 48 koans, compiled and provided with commentaries and verses by Mumon Ekai (Chineses: Wu-men Hui-k'ai, English: Wu-men or Mumon or Ekai). The text was first published in China in on the 5th Nov 1228 when Wu-men Hui-k'ai was a head monk at the Lung-hsiang (J. Ryusho) monastery.
General structure of cases within the koan collection:

The Case
Commentary by Mumon
Capping Verse by Mumon

1. Joshu's Dog
4. A Beardless Foreigner
7. Joshu Washes The Bowl
10. Seizei Alone And Poor
13. Tokusan holds his bowl
16. Bells And Robes
19. Everyday Life Is The Path
22. Kashapa's Preaching Sign
25. Preaching From The Third Seat
28. Blow Out The Candle
31. Joshu Investigates
34. Nansen's No Way
37. Joshu's Oak Tree In The Garden
40. Kicking The Drinking Water Jar
43. Shuzan's Bamboo Spatula
46. High Pole
49. Epilogue By Mumon

2. Hyakujo's Fox
5. Kyogen Mounts The Tree
8. Keichu's Wheel
11. Joshu Examines A Monk In Meditation
14. Nansen Cuts The Cat In Two
17. The Three Calls Of The Emperor's Teacher
20. The Enlightened Man
23. Eno's Good And Evil
26. Two Monks Rolls Up The Screen
29. Not The Wind, Not The Flag
32. A Philosopher Asks Buddha
35. Two Souls
38. Goso's Buffalo
41. Bodhidharma's Peace Of Mind
44. Basho's Staff
47. Tosotsu's Three Barriers

3. Gutei's Finger
6. Buddha Twirls A Flower
9. A Buddha Before History
12. Zuigan Calls His Own Master
15. Tozan's Three Blows
18. Tozan's Three Pounds
21. Dried Dung
24. Without Words, Without Silence
27. Nansen's No Mind No Buddha
30. This Mind Is Buddha
33. Baso's Neither Mind Nor Buddha
36. Goso's No Word No Silence
39. 39_Ummon_and_trap_into_words.txt
42. A Woman Comes Out Of Medidation
45. Who Is He
48. One Road Of Kempo

This page and pointed ones are a mix of sites http://www.angelfire.com/electronic/awakening101/mumonkan.html and of http://www.ibiblio.org/zen/cgi-bin/koan-index.pl.
There seems to be many on-line versions of this document.