I have a blog that I use for two purposes, the first being exactly what what cariad does. I am quite introspective, and seeing how I change has always been interesting to me.

The second way I have been using my blog is as a reference to programming and mathematics. Since I spend all day in math and programming classes, a lot of little interesting ideas will pop into my head. Thus I have lots of psuedo code in there so far. I am also entering the creative and unique pieces of code that I write for class so that I might be able to look back and see how my programming has developed. For example (and because I want to show off I guess):

Code:
                        
for(int j = 32; j > 0; j >>= 1)
    if( encoded.get() == 0x31 )
        current_code |= j;
In regards to BDSM, what if the Dom had the sub writing about their daily events and activities to encourage reflection on the relationship? Probably more helpful if the sub was just learning about the lifestyle, but they would have all those memories to look back at fondly.