You may have seen sticky threads in mailing lists like Google Groups which always stay on top of the archives independent of the date when they were posted. All new items will appear only after these sticky posts.
Technically, a blog is a kind of website that "displays posts in a reverse chronological order" - so the older stories are pushed down the order as new stories are added with time.
Why we need sticky posts on blogs ?
You may find sticky posts on blogs handy when there's an important announcement or say you want to highlight a particular blog post at the top.
Sticky posts are helpful in cases when your blog has been slashdotted / digged / lifehacked - you would like the flood of new visitors to see your most popular posts first as it may increase their chances of subscribing to your blog.
What's the hack for sticky posts ?
The idea is very simple - Change the date & timestamp of your blogpost to something in future or you may do the reverse and set the date to wayback in 1900s if you want your blog story to appear at the end of your archives.
How do I change the date / time in my blogging platform ?
For blogger [aka blogspot] - save the post as a draft or if you like to make an existing story as sticky, open in it Edit view.
The Date and Time settings for a post are beneath the post-editing field. Change the values to a future date,and publish your post.
For Typepad - On the Edit Post page, click the clock icon and edit the time and/or date of the post you can use the arrows on the calendar to navigate previous and next through the months.
For Wordpress - thought Wordpress lets you modify the date of a blog post via the "Post Timestamp" setting, it won't create a sticky post as the post will not appear on your wordpress blog before that date.
Luckily, there's a wordpress plugin called Adhesive that lets you turn any blog post into a sticky one. If more than one post is sticky, the post with the latest post time will appear topmost. Thank you Ryan.
A limitation of Adhesive is that it creates sticky posts per category. So if your stick post is in the "google" category and you're viewing the "yahoo" category, the stick post will not appear.
For Windows Live Spaces [aka MSN Spaces] - Windows Live spaces doesn't provide a direct way to modify the data and time of your blogpost but we can use the free Windows Live Writer to change the date of any of your blog post on Windows Live spaces.
Open the existing post or compose a new post in Windows Live writer and click the Post properties button on the toolbar [next to the spell check button].
A properties windows will open in the footer of your post where you'll find a calendar control to modify the date timestamp of the blog post. Choose a future date and post to weblog.
It may not be possible to change the date and time in your Xanga blog but if I discover a workaround, will definitely update this post.
Related: More Windows Live Writer Hacks, Better Google Rankings