For quite some time I was having a question in my head about "how to keep the data on a flash drive in a secure way?". It's also nice to have some small applications on the flash drive as well, Total Commander, for example. For that, I must carry the license file on the same flash drive as well. The same is true about the documents. I also want to make sure that the documents that I put on the flash drive are securely stored and if I lose the flash drive, no one could open it. For that reason I bought a U3 flash drive that has U3 security system on it. A couple of weeks ago, I tried to search if there are any alternatives for this type of security that would not be hardware dependant (U3 security system will only work on the drives that have U3 hardware in them), so I could put it on my MP3 player as well or lets say my 40GB external drive. I discovered quite fast that there is a way for that and that is what people do at portableapps.com.
Although both of them (U3 and PortableApps) serve the same purpose, there are quite a few differences between them. Here is short article that compares them. There are some other differences between them such as U3 system not having exe files stored on the disc but in special compressed format. Another difference would be the way files are actually executed (U3 will extract the files to the temp directory on the hard drive while portableapps will run it right from the usb stick). Anyways, both systems are quite good and it is worth considering if you are planning to buy a new usb stick or you have one and want to have more security there rather than just compressing your documents with the password. And you can always install portableapps on your older stick to enable security.