This is a mission that I believe should have been in the Clone Strike Ultimate Missions book, as it really is one of the most important scenes in the first trilogy. I made custom rules that I believe captured the most important parts.

To make the course of the pod race, put together the Korriban, Crystal Caves of Ilum, Rancor Pit, and Blank maps respectively. Other maps may be used, and you may increase/decrease the number of maps used to vary the length of the race.

The racers are: Anakin Skywalker (Youngling)
Sebulba (Dug Fringer)
Mawhonic (Gran Raider)
You may add/remove characters to match the number of players. For example, if you have 6 players, you can add a Rodian, Quarren, and Mon Calamari, or any other alien minis.

Victory Conditions: Make it from the first square of the first map to the last square of the last map!

Before the game, all the players must agree on where to place 2 Tusken Raider Snipers on the course. They must be on the Rancor Pit map and they must be in a walled section (canyon), though they don't necessarily have to be adjacent. If all players agree, you may play without Tusken interference at all.

Take turns placing your mini on the first row of the Korriban map. To work out the order, just roll a d20 and place them one at a time from the highest roll to the lowest. Once everyone is placed, it's time to roll for initiative!

Since pods are pretty fast ( and to make it more of a race), instead of having Speed 6, the pods have variable speeds. Each round after initiative, each player rolls a d20.
If the result is:
1-5: Speed 6
6-10: Speed 8
11-15: Speed 10
16-20: Speed 12

The following rules apply to the podracers:

1. Moving left or right costs 2 squares of movement.
2. Ignore difficult terrain. Low objects still cost double.
3. Racers may not fly over eachother; you must go around others.
4. Racers may not attack.
5. Racers can replace their attacks to attempt to force opponents to the side. To do this, they must move adjacent. Roll a d20.
If the result is:
1-5: The two racers' pods are locked! (More on that rule later)
6-10: Move your opponent 1 square to the side.
11-15: Move him 2 squares.
16-20: Move him 3 squares.

If a racer is locked with one or more others, it may replace attacks to attempt to break free. Both racers must roll a d20, adding their attack rating to the total. Whoever gets a highest total may continue moving as normal. The other(s) must move at half speed on their next turn.

The Tuskens mentioned earlier must attack the nearest target at the end of the round after a racer makes it onto the Rancor Pit map. If a racer is hit, its speed is halved for the next round. It may avoid this effect with a save of 11.

EDIT: Forgot to add this bit earlier. You can also add a lap or two to make the race longer. With this rule, racers who pass the last square of the last map may use up the rest of their move, starting from the first square of the map.

If all players agree, you can spice up the race by having prizes. You could all put in an entry fee and buy a booster or two for the winner. To make it really interesting, each racer could put one mini in a prize pool, making sure each mini is about the same value. Whoever wins gets all the minis in the prize pool!

The possibilities of modifications for your own pod races are endless, so have fun adding extra twists, changing the characters, or taking away some rules!