Yep, I had a similar problems when deciding to write a blog. First of all personal stuff may not be important/interesting to others OR maybe you may not feel comfortable putting too much personal details. I wrote a couple but always shut them down soon. Finally I started http://socialapp.wordpress.com

I have been going to a lot of meetups in the Social Space (Facebook, Myspace, Web Startup's etc) as my side projects/interests lie in the same area. In the process of these meetup's I have learnt a lot and seen a couple of good demos. So, I started to blog about those events or the demos that I see there for everyone else's. After any meetup, I typically have a descent number of topics to write about.

The primary reason for me to start a blog was to get better in writing skills and convert the thought process to text that fellow reader can comprehend. I am not really looking to make any money via blogging at least in the near future.

Another theme I have seen is that a couple of people write on funny incidents that happened to them during the day or weekend. It could be a funny/embarrassing incident, but they do a great job of expressing it that even strangers will find it amusing to read it.

Edit: In the process I also opened a twitter account (@socialapp) to see if I would be able to promote my blog. It's been a descent passive experiment as well =)