Simple gogle search will give you the download link 

http://www.google.co.uk/search?q=RX-51_2009SE_20.2010.36-2_PR_COMBINED_MR0_ARM.zip

It is week 36 build 2

File name: RX-51_2009SE_20.2010.36-2_PR_COMBINED_MR0_ARM.zip

MD5: b9f8690318a3be61767826d15b8c1784

SHA1: 54c9e5d6491ea73f9f4131c9f19cc01f9934fcdb

Update: See post http://nolovelust.com/post/Nokia-N900-PR12-Officially-Released.aspx for official relese of PR1.2

It took so long but it leaked :)

File name: RX-51_2009SE_10.2010.12-9_PR_COMBINED_MR0_ARM.bin

MD5: 013f4466e5899a9da0c34d5fa6b49b0c

SHA1: 6bb73a3cdcaf34ae5b7a7a4c3cba08b23ea1c058

Apparently it is RC of PR1.2 and was posted to http://talk.maemo.org then got deleted around after 12 hours by administrators due to it being unauthorized distribution.

You are probably looking for download link too but I can't distribute it here. Try usual places  

Please note that according to tweet from nokia conversations it will damage your phone http://twitter.com/nokconv/status/13299314191