Given: you, as DM, want to support these actions, and you want them to be pretty cool, but not imbalancing.
Given: You want the capability of this being used as an agressive act.
Given: You want use as few house-rules as possible.
As a simple mobility enhancer, the idea of long-jumps has been well articulated by jumping monsters like the Deathjump Spider. Therefore, whatever movement we grant, we'll describe it as a shift X.
Tossing a Halfling is fundamentally a feat of strength or athletics, except in the case where it's an attack. Using the jump rules seems perfectly appropriate as multiple characters are sacrificing their move actions to give one character a move.
Therefore, a Halfling toss that is not an attack requires a move action from the tosser and some way of spending a move action from the toss-ee. Having the toss-ee land prone is the simplest way of requiring both parties to spend a move action. The toss-er must make an athletics jump as per a moving long-jump, using the exact same rules and enhancements. (Keeping rules the same is a good thing. The sacrifice of a move action to do this is sufficient for balance.)
In a combat sense, things become more tricky. Specifically, we want this to be a viable alternative to both characters spending their standard action on an at-will. We also want this to be cool. If this requires 2 checks to succeed, it should hit as if both targets had hit.
Therefore the idea of the Thrown Charge. The thrower must ready an action (thereby spending her standard action) to throw the target. On the target's turn, he/she must take the charge action as normal, moving through the thrower's square. The thrower makes the "running jump" check as normal. For every excess square not needed in the jumpcharge, the target gains a bonus to attack and damage.
The calculations follow:
A normal MBA should do HP/8 damage: At level 1, this becomes
(8+24)/8= 4 damage. A successful throw at level 1 should therefore be able to contribute 4 damage on top of the "charge" (not worrying about charge optimization for now.)
At Level 30, the "generic MBA" should be
We will assume the normal "chucking" distance to be 4 squares, which is tactically significant because it means the ability to throw the small character past a brute-battleline.
This requires a DC 20 check. At level 1, a trained strength based character will have a +5 (trained) +4 (str bonus) = +9
50-50% is just right at level 1.
At 30, +15 (half-level) +5 (trained) +8 (str) = 28 base. Which is appropriate for an epic level character. Average check of 38 or 7 squares of movement.
The attack expression at level 1 for the throwee is:
(Assuming a +4 in their primary stat and a +2 proficiency weapon, +1 charge bonus)
In order to get the damage bonus we want, a +3 to attack and damage is necessary. This feels wrong, so we'll say a +2 to attack, +2 to damage for every unnnecessary square of jump, with a +2/+2 for simply getting there.
At level 1, this is: 50% of the time, insufficient distance. 25% of 8.05 (exactly 4 squares of jump), and 10.8 (5 squares of jump) for a really good athletics check. A very acceptable trade, statistically speaking, for a fighter who wants to chuck the halfling at the back lines.
At 30, this same progression at 4 squares (laughable at level 30, but...) Versus an average of a 7 square jump check gets: +4 to hit /+8 damage.
(Attack roll of 15 (half-level) 8 (stat mod) 3 (weapon expertise), +6 (enchantment), +2 proficiency +1 charge for a nice 55% hit rate on the bloody treadmill.
(1-(14+30-(15+8+3+6+2+1))/20)*(2*5.5+8+6)=13.75 Or "hahahahaha" damage. Adding, +8/+8 onto that gives us 31.35 which gets the charge into non-pathetic damage numbers. In epic, where most people have fly, teleport, or shift whatever, this technique will never be used, but it will probably be used in mid-to-high heroic and low paragon and it seems to scale appropriately.
Visually, the idea of the huge guy kneeling down with hands cupped into a stirrup and the tiny guy charging is quite compelling, especially with the tiny guy hitting for a decent amount of damage as a consequence of them coordinating.
With a simple bonus added to the normal long-jump rules, all of this falls neatly out of the rules and provides an interesting alternative to attacking with one's standard action at any level of play.