1)In WL 8.x we have connection pools and data sources, 
where as in WL 9&10 we have only data sources and inside 
data sources we are having connection pools.
2)In WL 8.x we ahve execute queue's, where as in WL 9&10 we 
are having work managers.
3)In WL 8.x we dont have LOCK & EDIT, Where as in WL 9&10 
we have LOCK & EDIT.
4)In WL 8.x licence.beafile is present to update the 
licence,Where as in WL 9&10 there is no licence.bea file.

All the above is correct except for #4.  You do need the
license.bea for WL 9&10.  The difference is that there is a
generic license.bea file for each version that you can
download from Oracle.  No need to request a custom
license.bea file.  In WLS 10 MP2 and above, the downloaded
software comes with a fully blown license so no need to even
download a new one from Oracle.

I am adding some more points:

5) In Weblogic 8.x, all the jms details will be present in 
the same config.xml whereas 9.x/10.x it will be partly 
maintained in config.xml and a separate xml files in 
domain/config/jms folders for each jms module.
6) In 8.x we don't have concept of JMS modules and 
subdeployments whereas its in 10.x.
7) In 8.x, we have queues,topics,distributed destination 
etc., separately whereas in 10.x they are clubbed inside a 
JMS module.
8) The directory structure inside a domain differs alot 
between 8.x and 9.x/10.x like the config.xml location,cache 
and staging folder paths,managed or admin server paths etc.
9)The wlst is made more easy and comfortable from 9.x 
onwards when compared to 8.1 sp6.