The first blog is Dennis Yurichev's who is a reverser and a security researcher. There are some interesting posts, particularly the dumps from the Oracle binaries that show "probable" function calling sequences in the Oracle library. Useful if you want to see some sort of heirarchy or match to a trace created with a tool such as truss or strace. I have known Dennis a long time via email so its nice to see him start a blog
The second blog is that of Miladin Modrakovic whom I have also known via the net for a ling time due to him asking me to publish some of his papers on my site around direct SGA attaches and also oradebug use. The links and papers are in his new blog posts so have a browse.
Both blogs have a slightly different focus but both firmly around internals, along with Tanels blog we now have the promise of some great internals info.