These are tools and resources that I use on a regular basis and would recommend to anyone. Keep in mind that I'm an affiliate for some of these products/services and earn a commission should you choose to purchase them.
If I had to choose one internet tool, I would choose a scheduler. If I had to choose one scheduler, I would choose Acuity. It is simple, ultra convenient for your contacts, syncs with your calendar and can even embed in your website!