Equivalent to Sysinternals Process Explorer on Linux

If you don't mind something that's terminal based, then htop is a good and powerful process manager.

You can install it on Ubuntu with the following command:

sudo aptitude install htop

If you prefer something with a GUI, you could try qps.

You can install it with the following:

sudo aptitude install qps

Use Linux Process Explorer.

Graphical process explorer for Linux. Shows process information: process tree, TCP IP connections and graphical performance figures for processes. Aims to mimic Windows procexp from sysinternals, and aims to be more usable than top and ps.

PS. it is still in alpha development stage.

gnome-system-monitor

(although i don't know what the OP needed 3 years ago)

gives almost everything that "top" has, but graphical, sortable columns, find open files, and more.

Few screenshots:

Resources tab: