How many posts or how long should the home page of a blog normally be. Is there any search engine benefit to having a home page with more posts? Thanks.
If your posts are unique it should not matter. If you are doing automatic blogging you should keep many posts at the home page to at least keep it kind of unique.
In terms of SEO more is better, BUT you're designing for your readers not search engines, so find a medium ground, somewhere between 10 and 15 depending on how long your posts are.
I'd say it depends on how often you post and how many return visits you get. leave enough to save readers the hasstle of hunting through the archives for yesterday's posts... but don't make it so long that you've got stuff up there from last month. Again, this depends on how often you post. If you've got an automated blog just dump it all on the front page. Limit it's size for download speed though... keep it under 50k if you can but don't sacrifice it's quality/quantity.
My posts are long, I set it at 3. I see blogs with short posts (3 or 4 lines) set it for 5, 8 even 10.
Its better to keep the number of posts down. You want the actual post url to rank high not the index, category or archive page. Your main page will rank high anyway as its the root of the blog where your whole blog will link back to. If you do have a high number of posts or even long posts on the homepage use the <more> tag after the first paragraph of the post, this will help keep down the amount of duplicate content on your blog.