Showit provides basic contact form options which allow you to create any form fields you'd like your site visitors to fill out. However, you may find that you need additional functionality like dropdowns, checkboxes, or the ability for visitors to upload files.
Once you've selected the right platform for your needs, just embed the code via these instructions.
Google forms is a great and totally free option for all google users! You can do a lot with these forms and it's a great solution for basic form needs if you're looking for a free option.
Embed social provides a wealth of embeddable widgets and features for any website. They have a free plan option which is shown below and you can see all plans here.
This option is again a platform with many customer funnel-related tools from lead generators to customer funnels and online forms. They have a totally free plan which is shown below and you can see all plans here.
This is a platform focused on forms and collecting visitor data for your website. They have a free plan shown below but you can see all their plans here.
Jotform is another form-focused platform for your website. Their free plan is shown below but you can see all their plans here.
Cognito Forms is another great form provider with a free option which you can see the details of below (more details available on the pricing page). You can see all plans here.