See how I put "Thursday" in the title there, as though I've done this in the past or will ever do this again in the future? It's a tradition that starts and ends today; you can consider this post endorsed by the weight of a mythical history of repetition.
Anyway, a few browser games to entertain you which you may or may not have encountered before.
Hedgehog Launch is a neat little thing which challenges you to fling a hedgehog into space, using a combination of elastic bands and jet engines. Your first few attempts will be pitiful, but over consecutive days you accumulate cash with which to upgrade your elastic and/or engines. Surprisingly fun.
Splitter is a physics based game which presents the classic challenge of moving a ball into a hole. The catch is, the only way you can interact with your environment is by cutting things in two, and you only have a limited amount of cuts. Very neat.
Finally, Shore Siege is a defence-style game where you play a crew of shipwrecked pirates struggling to repair their vessel while being attacked by waves of enemies. In addition to deploying snipers and turrets, you take an active part by using a pin to pop balloons, a fire to burn marshmallow-enemies, water to douse fireballs, et cetera. Addictive.
All of the above links point to Kongregate, which is my way of attempting to get sweet, sweet referral points for that site, but I should mention that Shore Siege and Hedgehog Launch are the work of Armor Games and if you particularly like them you might want to visit their site directly.