free Tools to monitor website performance

Hi All, Thanks to all for reviewing my topic, may it is slightly off topic. We have almost 300 URL's (local and web) and we want to monitor few of them which are very critical URL's for web access and local access. I would like to know is there any free tool or software with I can use to monitor url performance in terms of response time. Which gives more information like how much time it taken to connect the server and time to load the page and total response time. Thanks in advance. -- With Regards, Sathish Ippani