Searx seems to have categories such as music, science, news, social media and so on which is better than nothing.
What I currently do is: (site:blogspot.com OR site:livejournal.com OR site:wordpress.com) <query>
Blog search gives me pages written by people: fans, amatuers and sometimes professionals; I miss such pages and perspectives when I do a general web search in Google. Above search, however, excludes self-hosted blogs and other hosting services. For forum search I just add something like phpBB|vBulletin|Invision to the query which is a hit or miss. I also have Google CSE created from my 500+ RSS feeds which gives very good results.
Earlier Google used to have both these features and it is annoying to see they remove useful functions. I just hope someone comes up with a search engine for blogs and discussion forums.