Are there ways for a character to employ forced movement without using any powers, feats or items of the sort? By that I mean using exclusively skill and ability checks.
The Bull Rush is the first thing that comes to mind when you ask this question. (I think Brian Ballsun-Stanton's comment is foreshadowing this), which requires a charge attack.
Beyond those, I can't find any untrained ways to move someone (IE powers, feats, etc.) short of Bankuei's reference to DMG1, p42 for improvised actions, the example of which includes a push type action.
D&D4E's pg. 42 of the DMG has guidelines for stunts. The general gist is that as players come up with random stunts, the GM can assign a stat to attack with, a defense stat for it to go against, an amount of damage, and conditions.
"I roll a barrel down the stairs at the goblins" - could/should easily result in forced movement (down the stairs).
Of course, this depends on what objects/terrain is available, the monster(s) you're fighting, and the GM's ruling about each particular stunt you're doing.