我想今日辭職,辭職信點寫?

Do you mean in English? 因你尚在試用期間, 故可較簡單點:
Dear Sir,
I regret that I have to resign from my present job & effected immediately. During the duration, I really enjoyed & learned a lot from this company. Thank you.
Yours sincerely,
xxx
Date
Note: You are not entitled to get a referrence letter from a company which you resigned during probation period.

親愛的(上司名字)：

本人已決定辭去現時(職位名稱)的職位，並由即日開始即是x月x日正式生效。

在此，感謝(公司名稱/ 貴公司)給予本人學習的機會，並取得寶貴的工作經驗。希望本人的離識不會為你帶來

很大的不便。本人希望在離職之前，能夠取得離職通知書。

祝工作愉快!

2008-05-06 11:32:39 補充：
你必須睇清楚合約規定,有好多公司都是做滿一星期至一個月之內,就要雙方七日通知!