I took a 5,000 nautical mile, 45-flight-hour cross-country trip in a Cessna 177 RG (Cardinal) in August of 2004. You might want to start at part 1, if you haven't already read it.

Tips for Pilots

First and most important -- Get an instrument rating :-). People's sensitivities vary on this issue. I know some pilots that have no problem cruising along above a broken layer of clouds, with a plan of "I'm sure we'll find somewhere to get down eventually". I am just not comfortable with that kind of "plan". If you're planning to do the trip VFR, then, please do at least expect to spend 2 weeks doing it, and don't be afraid to sit in one place for a day or two waiting for conditions to improve.

On to the rest of the advice (which is probably worth what you paid for it):

1. Start out by buying a JNCA-5 Planning Chart of the United States. Hell, they cost $4.75, buy a few of them. Plan a general route, but don't bother spending too much time picking out individual airports. Plans will change enroute! I spent hours picking out exactly the right route, even picking out Victor airways across the entire country... and when the trip actually happened, weather and equipment problems made my flight plan useless. Our very first stop -- Winslow, AZ -- was the only airport I had planned for in advance.

2. On a similar note, don't make hotel reservations anywhere. We never had any problem getting on-the-spot hotel rooms at any airport, from the smallest to the largest. Reservations only serve to limit your options. This can be dangerous: If you're feeling tired or the weather is marginal, a far-away reservation causes get-there-itis, pressuring you to continue. Conversely, if the weather is wonderful and you're feeling great, a nearby reservation prevents you from exploiting good weather by flying for an extra hour or two.
3. Based on your general plan, buy all the sectionals for your route. If you're IFR-capable (which I think you should be), also buy the IFR low-altitude enroute charts and books of approach plates for your planned route. I prefer the Jepp plate format, but bought the books of bound NACO plates. It was very convenient to have pre-bound books and easy to rip out the plates I needed. NACO plates also are much cheaper.
4. Don't be stingy when buying charts: if you come close to a chart edge, buy the next chart too. The last thing you want is to be stuck without the right chart or approach plate when your plans change. Remember, your plans can change in the air, e.g., for a deviation around bad weather. I spent a total of about $200 on charts for this trip (JNCA + sectionals + IFR enroute charts + 12 books of NACO plates).
5. It's useful to have an AOPA Airport Guide. It's one book that has information about every U.S. airport, including phone numbers for cabs, hotels and restaurants. In a pinch, just land at airports that are depicted on the sectional charts as having services (i.e., the 4 hatches drawn around the airport's magenta circle).
6. Before each flight leg, spend some time with your JNCA-5 and sectional charts, a weather depiction of some kind, and your AOPA airport directory, and pick an airport that is about the right distance away based on how long you want to fly. Then call Flight Service for a briefing.
7. Everyone has this advice but I'll say it anyway... avoid flying over the high deserts of Arizona and New Mexico in the middle of a summer afternoon. At best you'll get an exhaustingly bumpy ride; at worst you'll be surrounded by thunderstorms. Don't take off with full fuel; fly shorter legs instead.
8. At high-density altitude airports, your groundspeed is much higher than normal for a given indicated airspeed. This is common advice, so I kept thinking, "I just watch the ASI, and fly the approach at normal indicated airspeeds". Well, that's fine for avoiding stalls or mushing, but what I forgot was that you need a much higher-than-normal descent rate on the VSI to achieve a normal descent angle at that groundspeed. I never came close to stalling, but often came in way too high. It's disconcerting to see a -1000fpm descent on final, but, when your groundspeed is 110 knots, that's what you need sometimes.

9. In an area of bad weather, call Flight Watch early and often. Even after you finish the conversation, continue monitoring the frequency. They may call you back with updates. Or, you may hear other pilots requesting information, or reporting on the current state of the weather as they see it.