I had used 続ける.jp until several days ago but I stopped using 続ける.jp.
Because, I had found more usefull one.
It's "Don't Break the chain".
I found it via idea*idea(http://www.100shiki.com/archives/2007/09/dont_break_the_chain.html).
A most important reason that I changed to it is that it enables me to check a day even if the day has passed.
But there are other good features.
For example, It can be attached to blog as blog parts. It can be seen as calendar.
Accordingly, let't use "Don't Break the chain" ;-)