Accepted PostgreSQL compatibility patches:
phbBB2Drupal
relationship
organic groups
workflow
core 4.7.2: node.module
Masquerade
OG Block Visibility
CCK: unsigned int columns
subscriptions
flatforum
gallery: upgrade blocks table UPDATE fails
masquerade: cron query fails in PostgreSQL
unitag

Accepted patches, other:
phpbb2drupal comment thread numbering
comment_mover: reversed order on patch, thread numbering fix

Not yet accepted patches:
Mollom: PostgreSQL compatibility: Was here, gone now...
core: comment: thread IDs grow too fast

Helpful Bug Reports
Subscriptions: PostgreSQL: error with group by when adding/saving a node - fixed in 6.x-1.5.

...as of 2012-05-31.13 EST.