I use "The Journal" available at http://www.davidrm.com/thejournal/. Definitely worth a look - they have a full-featured 45 day trial you can download.
I was looking for such a program for quite a while but was really limiting myself by requiring that the application have both a desktop PC and Pocket PC version available. But I finally gave up on that and started looking for simply the best PC journal software I could find - and The Journal fit the bill. Excellent developer support with a very active Yahoo group (though I don't really like Yahoo groups!). This one gives me all that I need, plus has a lot of additional features that I am not presently using, but I hope to use someday.
It's not inexpensive, but it satisfies all of my requirements, and has some extras that are really great.
Oops - I just noticed that superboyac did mention this software in his initial post -- and he is correct in that this application is not really interactive with other applications, though you can link a number of other document types to it, as well as embed them in your journal pages.
I posted this originally two and a half years ago, but I am really starting to sour on this program. I am probably going to uninstall it and reinstall the previous version, The Journal 4. The latest version, 5, which was five years in the making, was a big step backwards, IMO. No new features, believe it or not. Well, there are some under-the-hood changes which I can't see as useful to me at all - like a journal file can now be >2 GB.... So.....? If mine ever gets that big I will have spent way to much time writing in it! Especially since it doesn't really accept photos in its journal entries easily.
The main changes were UI-related. Big, puffy, 3D icons on the toolbar which are so hard to read that many users are requesting the ability to return to the old toolbar styles. Also, he added skins, which in my opinion does absolutely nothing to improve the product. So what I now have is the same basic functionality that i had in the previous version but much slower and uglier.
So I am hunting for a good replacement, hopefully one that is actually developed.
I did purchase the Smart Diary Suite
when it was offered at a big discount on Bits a few weeks ago but I'm not too impressed with it so far. Hopefully this thread will pick back up and I can get some good recommendations.