Are there any good R object browsers?

Question

S-Plus has a great object explorer and data editor built into its GUI. It allows you to easily see all the objects in the workspace at a glance, and sort them by name, size

Answer 1

The lsos() function shown in this SO questions is also a primitive object browser:

R> lsos()
               Type  Size Rows Columns
ls.objects function 11792   NA      NA
lsos       function  1112   NA      NA
s           numeric   824  100      NA
y           numeric   184   20      NA
x           numeric    56    3      NA
z           logical    32    1      NA
R> 

Answer 2

RStudio has a nice object browser.