"Re" - meaning again, back, anew
* Re-arrange: to organize something in a different way
* Re-build: to build something again
* Re-cycle: to process used materials for reuse
* Re-enter: to enter something again
* Re-write: to write something again
* Re-imagine: to think of something in a new way
* Re-think: to think about something again
* Re-claim: to take back something that was lost
* Re-wind: to move back to a previous point
"Un" - meaning not, opposite of
* Un-happy: not happy
* Un-certain: not certain
* Un-fair: not fair
* Un-likely: not likely
* Un-able: not able
* Un-believable: not believable
* Un-prepared: not prepared
* Un-aware: not aware
* Un-lock: to open something that is locked
"Dis" - meaning not, opposite of, apart, away
* Dis-agree: to have a different opinion
* Dis-appear: to vanish
* Dis-connect: to separate something from a connection
* Dis-like: to not like something
* Dis-courage: to make someone less confident
* Dis-continue: to stop something
* Dis-able: to make something unable to function
* Dis-empower: to take away someone's power
* Dis-please: to make someone unhappy
This is just a small sample of the many words that use these prefixes. You can find many more by browsing a dictionary or online word lists.