currently it's 188.8.131.52.4 Patch Set Update (PSU)
please check Oracle Recommended Patches -- Oracle Database [ID 756671.1]
also Release Schedule of Current Database Releases [ID 742060.1] is of some interest.
I assume by applications you are talking about Oracles E-Business Suite?
There is another master document about PSUs: http://www.oracle.com/technetwork/topics/security/alerts-086861.html
It leads you to PSUs for the database, EBS and other products.
It is not needed to have all Applications on the same PSU - and there are often requirement for several Applications which need additional patches installed.
To check which PSU is applied at DB level, you can run at OS prompt
and with aql*plus
select ACTION_TIME,ACTION,NAMESPACE,VERSION,BUNDLE_SERIES,ID from registry$history;
But the link having(http://www.oracle.com/technetwork/topics/security/alerts-086861.html) details about the CPU
Since I am looking for PSU related things,I want to know on which PSU my E-Business suite is running,can my
applications be updated to the latest available PSU release.