I use 4 of the steel ramps that were shown above.  When I strap them together and ratchet it down just a bit, it makes a very solid wide ramp that enables walking a bike up or riding it up, either way it is pretty easy depending on  the angle you are having to deal with.  Like Dave said, even just a foot or two up on the back end can make a big difference when loading.  
By the way, these  are the longest ramps that do not fold I have found.
These ramps are made of heavy steel and are extremely strong.
When I take a trip anywhere, I take my ramps with me.

Thanks, all. Sounds like the Harbor Freight ramps are the ones to get, assuming they will work with my friend's Tundra. I'm not clear on how to determine whether the bike will get hung up when going up the ramp. What should I be measuring?

Here's a short video of me loading my S40 in the back of my chevy S10. I used a pair of ramps that I bought at a local discount store for about 50 bucks and bolted them together giving me about a two foot wide ramp that has a lip at the top. I also used two 2x4's as outriggers for my feet. I never had any problems loading and unloading by myself. Plenty of clearance, never bottomed out at the top.
Good Luck, AL
https://vimeo.com/25628093

Thanks. Looks pretty easy (when you know what you're doing). Are those 6' ramps?