<p>If I make two iPhone applications, how can/should I share custom data (not contacts and stuff like that) among them?</p>

<p>Thanks!</p>

There are two different ways you might go about this.
1) The data you need to share is non-persistent. In other words you need to launch one application with a piece of data that it can do something with. In this case you would register a special URL scheme per application.
You can find out more information about URL schemes via Craig Hockenberry in his
[redacted] blog post
.
2) The data you need to share is persistent. In other words you need something like a data file that both applications can read and write too. As far as I know there isn't a safe way to do this other than storing your data on a remote server. If you need the data accessible without a data connection then you would need to figure out a way to sync data between the individual apps and the remote server.