Readings & Meanings:
He laughed at me.
He greeted me with a smiling face.
Good fortune comes to a smiling house. (expression)
笑 has a bamboo crown, otherwise known as a Take-Kanmuri.
夭 is a pictograph of a "slender, limber youth" (see Kanji Network ref. below).
Weirdly, this character came to take on the meaning of a different character, and that's how it acquired the meaning of "to laugh, to smile." Its history is intertwined with 咲, which is somehow related to the expression "鳥鳴花咲" from the Chinese.
I've seen this in blog posts, emails, and IM chats so much that I don't even see the kanji anymore, I just see two eyes above and a smiling mouth.
When a Japanese person wants a way to show that they are laughing or not serious, they don't use ":)" or "lol." They tend to use "(笑)" at the end of their sentences.
おかしい is always written in hiragana, but the kanji is 可笑しい.
一笑百花香 is a very rare expression, found by one source in a rural museum of calligraphy (in Nagano). It has very simple kanji. Can you guess what it means? Answer in the comments.