You can try it out now at GoJournalApp.com.
The easiest way for me to summarize it is to just copy-paste the help page right here.
Write #awesome things and tag use hashtags to find them later.
Find things by hashtag by typing only the tags you want to search.
Have something to do?
TODO: write todo's in your entries.
DONE: and click them to check them off.
ALSO: notice you can use "todo" or any word you want.
Like searching for tags, you can also search for todo items, or whatever word you used. You can even mix them with hashtags! Here's how I find a list of books i want to read.
Finally, while you are searching, anything you write gets the current hashtags automagically
You can use this to create separate notebooks, topics, or any other way you want to organize.