Sitemaps are a useful tool in helping get your blog pages indexed by search engines, which gives your blog extra "visibility" online and can drive more traffic to your site.
Unfortunately, it can be quite difficult to hand code a sitemap file for a blog, especially if you have a lot of posts! Also, you would need to have your blog's sitemap hosted in the root directory of your hosting account, which makes it impossible for Blogspot bloggers to achieve.
There are ways for for bloggers to solve this problem, and create sitemaps which can be indexed by Google and other search engines. Here are some suggestions:
Blogger:
The easiest way to upload your sitemap to google is to use the atom.xml file which is automatically generated for you. This will be located at: http://yourblogname.blogspot.com/atom.xml if you have a Blog*spot hosted blog, or at http://www.yourdomain.com/atom.xml if you have a custom domain.
I've also found this tool by Stephen Newton, which is a template you can use temporarily (don't publish, whatever you do!) create a sitemap which can be saved as an XML file if you have your own blog hosting (or some free hosting with your custom domain). Full details can be found over at Stephen's site.
Moveable Type:
Niall Kennedy has created this great template file which you can use to create an XML sitemap of your Moveable Type blog. Copy the code into a new index template and save as "sitemap" or something memorable. Once your sitemap template is saved, you can tell Google and other search engines where it is.
TypePad:
You can choose to publicise your sitemap in the settings. To add a sitemap to your weblog, go to Weblogs > Configure > Publicity and select Yes under Google Sitemap for your Publicity Preferences. More information can be found here.
Wordpress:
Arne Brachhold has created a great Wordpress plugin to generate a sitemap for Wordpress blogs, which you can find on this page.
There's also a useful PHP file available for Wordpress users in the Social Patterns blog.
General/Other blogs:
Pingoat have also created a dynamic sitemap generator which uses your blog's address and can alter the priority of your posts to let search engines know which pages are most important. Once you've created and saved your XML file, you'll need to save this in the root of your web directory.
Technorati Tags: seo | search+engine+optimisation | search+engine | sitemap | google | blogger | wordpress | typepad | sitemap+generator | xml