The simplest free tool, good enough to quickly create simple videos and images, add some transitions and text, comes with all Windows versions = Windows Movie Maker. The tool sucks for longer videos, as it is not very stable and often freezes when you have many transitions etc. But it toally does the job to add an URL on your video (= add text) or insert images and such. Good enough for starters and its free.
I am not a Mac user, but for Mac there is also a free basic movie editing software coming with the system.
If you want to mix up things automatically and let a slide show look pretty there are online video tools that are usually free for videos up to 30sec or so. You have to pay for longer videos or HD quality.
Examples: www.animoto.com or https://flixtime.com or http://slide.ly/ etc.
Those are more photo slide show creators, but you can also insert video portions. And they also provide you free music you can use on your videos, and that music tracks are royalty free (= you can use them on your videos without copy right issues)
A free video editing software option I have heard people talk about is http://www.nchsoftware.com/videopad/ - but I have never used it myself, so I cannot share any experience on that one.
For Screen Recording:
Like mentioned already, www.Jing.com is great for screen recordings, and free for up to 5min video legth.
Camtasia Studio is the big brother of Jing and a professional, and expensive screen recording video tool, about $300 - Jing and Camtasia a both from the same company = www.techsmith.com.
And then we have all kinds of various video editing software for cutting and editing your recordings any way you like, and add more nice effects, and price depends on features of course.
Sony Vegas Pro for example is a great one, feature rich and expensive. But may be overkill for what you need for video marketing. Smaller ones that do the job just great, including green screen / blue screen (chroma key effects), if you look into somethign neat, would for example be Magix products = www.magix.com . Personally I am for example using Magix Movie Edit Pro (about $69 if I remember correctly), which is feature rich and excellent enough for making really nice videos, transition and video effects, and at that price even has the green screen feature. Magix (www.magix.com) and Sony ( http://www.sonycreativesoftware.com/) products are pretty much the best, since audio and video products are their core business since years. Nevertheless you can google for other video editing options suiting your demands and budget.