I am creating an animated title screen and want to have the animation repeat a certain frame, so text can be shown for a longer period as if the animation had been paused before continuing the rest of the animation.
You can duplicate the desired keyframe(s) and move it further in the timeline. As it interpolates between those two points, the animation will freeze at that keyframe for as long as you specify.
As Puck suggested, you can duplicate keyframes to achieve this effect.
To do this, open one of the keyframe editors. I'd use the Dope Sheet view for this task since you need adjust the keyframes in the timeline, but don't necessarily need to change their location/rotation data.
Make sure to deselect all keyframes by hitting A. The keyframes will be white when deselected. Now select the keyframes you want to duplicate by hitting B and using your mouse to drag a box around them. The selected keyframes will turn orange.
Hit ShiftD to duplicate them and move the mouse. The keyrames will follow, so you can position them in the timeline. There will be an orange line signaling duplicated keyframes and the length of the pause the animation.
If you want to move the keyframes again, hit G to grab and re position them again.