Question: I see a lot of blogs that seem to have really cluttered sidebars, with a ton of additional widgets, navigation, etc, that I never find myself using. What are some tips for things that make good additions to the sidebar, and some things that are unnecessary? 

One example that springs to mind are Tag Clouds. I see these everywhere, but how often to people actually use them?

Answer: 
Maybe it's just me, but I *like* when a blog has a tag cloud. It lets me see at a glance what kinds of things the author talks about, and gives me a really easy way to browse the content that I'm interested in. I also like the archive links, if I've just discovered a blog that's been around for a while and I want to go back to the beginning and get caught up.

I agree, though, that a lot of extra widgets in a sidebar make me not want to visit certain sites that I may otherwise frequent. All of those things have to load and initialize, and that takes time and resources I'd rather not spend.
I'd say that the cleaner the side bar is - the better. 

My personal preference is to have there some info about the blog or the blogger, plus maybe a blog roll, which most people expect in the side bar.

I think tag clouds are usually useless and I'll explain:

* The context is too wide (the whole blog). It's much more effective to use the tags in each post to follow through to the topics that interest you.
* Often the most prominent word is the topic of the blog and since it appears on almost all the posts, it becomes redundant.
* Sometimes tags are abused for SEO purposes, so some might have weak connections to the actual content.