I've just finished updating the Mobile Science site there are now over 400 entries covering all areas of science. The latest entry is Notelus an electronic lab notebook (ELN). ELNs seem to be increasingly popular, and having access to your notebook on a mobile device that you can carry into the lab/library etc. is very attractive.

There are a selection of ELNs for iOS, some also have desktop versions, whilst there are other systems that are web-based and can be accessed from most devices.