Russell Beattie at Mobitopia talks about the applications on his phone:

So I'm starting to pare down the apps I'm using on my phone. With the 7650 specifically you really need to choose which apps you use wisely because there's just not enough room to store everything and choose later. So far, here's what I've discovered are the best apps which I have installed on my phone.

First the Symbian Apps:

Yellow FTP is the killer app of my phone. It allows me to upload/download any piece of data I want and was the first app to show me that my handset was a real IP connected computer. I use this app to upload photos to my Moblog directory on my server and to upload/download text files to read on my eBook reader. This really allows me to manage the space on my phone better and is the inspiration behind DotMob. This app cost $25.

And of course, there's much more