Get ready, Google will be updating Page Rank Algorithm in mid of July 2010.  This is the best time to get back links from trusted source which includes Articles site, Blogging, Press Release and might be link exchange with relevant site.

Here is more detailed information about Google PR Updates:

• Middle of April 2010 (Actual date April 3rd 2010)
• Middle of July 2010
• Middle of October 2010
• Middle of December 2010