I like the simplistic design, no bells and whistles just clear functionality.
A very quick and good example of AJAX. As you type the word the Dictionary begins matching the word. The live timing aspect is definitely something that catches the users eye.
The Bookmark feature for FireFox works well.
Dictionary.hm - Free Online Searchable Live Dictionary
Here is another cool Ajax site. Definitely in Beta mode, but worth a visit. I really like the layout although the earlier layout may have been a little more user friendly.
blabb works the way I would expect Ajax sites to work. You can search for tagged sites and then read the summary RSS or Expand it. You can also see a complete view of the site before visiting. In my mind this is one of the main reasons for RSS and Ajax.
A few more options and some instructions would be nice. It seems that once you select Yesterday or Today [...]
