Formal:
* Weblog (the original term)
* Online journal
* Digital diary
* Personal website
* Content management system (CMS) (technically, a blog is often built on a CMS)
Informal:
* Webzine (if it focuses on a particular topic)
* Online magazine (if it features various articles)
* E-zine (short for electronic magazine)
* Website (broadly, but not specific to blogs)
* Online publication
* Log (short for weblog)
The best word to use depends on the context and the specific type of blog you're referring to.