On LaTeX-Community.org I’ve read that the Identi.ca microblogging service provides blogs/groups about (La)TeX related subjects too:

• latex
• textsatz (in German)
• typesetting
• typography

Links to those groups were provided by Thorsten on LC.

In previous posts I’ve shown some examples how the TikZ graphics package could be used to draw mathematical diagrams like exact sequences and commutative diagrams. Felix Lenders has written a tutorial called Commutative Diagrams using TikZ dealing with this subject and has published it today. In that paper he’s describing basic syntax, styles, arrows, curves, positioning issues and more. The tutorial contains several examples with the corresponding source code.

To read related blog posts have a look at the TikZ category.