Speed up minecarts without using other minecarts?

For a while I used the (formerly) well known minecart boosters for speeding up other minecarts. Furnace minecarts are nice because you don't need typical boosters, but I don't think they can be triggered, can they? Are there other possibilities that don't involve using another minecart?

1.5

1. Powered tracks are now available in 1.5, and boosters were removed in 1.6. The powered tracks will accelerate a cart in the direction it is moving while the track is powered. When the track is off it acts as a break.

1.4

In the interest of maintaining a comprehensive list there are four primary ways of moving minecarts:

1. Physically pushing – it's slow, and boring, but it's one way of transporting lots of goods a great distance.
2. Gravity – It's a one-way method of transportation, but you can gain quite a lot of distance from a minecart track that's sloped correctly.
3. Furnace-carts – Furnace carts are wonderful for traversing flat terrain with minimal track-usage. Coal/Charcoal is quite common, and makes a furnace-cart a good way to transport goods remotely without using quite as much iron ore.
4. Boosters – The fastest way to travel, boosters are great for traveling really far, really fast. They do have some issues, however:
   • Boosters consume a lot of iron ore to create the carts/track that sit idle the majority of the time
   • Boosters may be removed ("fixed") in a future update, as they were an unexpected "feature".

Secondary Travel methods:

1. Hopping in an out of a minecart while moving to use the pushing effect to move at a reasonable speed.
2. Slimes & other NPCs – As mini-slimes are attracted to the player, they can move toward the player giving the minecart a physical push. Given the recent addition of wolves, it may be possible to have pets do the pushing. Zombies, and spiders may also be able to push the player, however the boost would likely only last as long as your life.