Only DVD+R can be overburned with current DVD burners (in addition to CD overburning of course).
Plextor drives have had this feature since at least the PX-712, and it is still present in the PX-760 (with firmware 1.02). The Plextor PX-755 might be able to overburn with a future firmware upgrade, but currently it can't.
BenQ DW1640/1650/1655 can also overburn, but they are slightly quirkier because you have to disable SolidBurn and you cannot overburn just a few MB - you have to overburn with a size greater than 4493 MB.
See this thread about BenQ 1650/1655 overburning.