The best way for me is to buy a Bengali Panjika. I buy either a Benimadhav Panjika or a Madana Gupta one for each Bengali year.
And, these books will have all the needed info, the kind of you are looking for and of course much much more.
Each such book will have a separate section called Vrata Prakarana, which deals with various Vratas celebrated by any Hindu throughout the year.
For e.g. Shivaratri vrata, Mangala Chandi vrata, Satyanarayana vrata, Itupuja vrata, Vipattarini vrata, Lakshmi friday vrata, Shanidev vrata, Janamshtami vrata and many others.
And, for each such vrata the necessary details related will also be given.
For e.g. for Shivaratri vrata they have given a list like:
So, the easiest way for you will be to buy a hard copy Panchanga for your own region. It will also have all details of everything needed to conduct a marriage properly as it is done in your region.
Which are the auspicious dates for marriage, Chudakarana, Annaprashana etc are also listed in all such Panjikas (Panchangas).
For online resource, you can check Drikpanchang.com. On this site you will get lots info about when is what vrata but the information found in a hard copy is much much more detailed.
For e.g. from this page you can find the list of various Hindu vratas. And as you click on the vrata you are interested in, you will find list of all the days of the year which are the vrata days.
As an example, here are the Sankashti Chaturthi vrata (a vrata dedicated to Lord Ganesha) dates for the whole year.