But it's still early days yet. Apple gave only a chosen few developers early access to the iPad -- everybody else had to make do with software simulators and homemade cardboard mockups. They rushed their apps to market, and it shows. Many of the early apps are buggy and missing features.
These are the best apps I've found so far. They are all iPad-optimized, not iPhone apps stretched to fit the iPad. They get the job done, they're fun to use, and several of them are free.