You can use most PPC engines both to make money by being their publisher or to promote your own sites. Here is a list of some PPC engines. If you know of one that I have missed out please let me know
---UK Specific PPC---
- Mirago
- Search123 (ValueClick)
----- A----
- Adhearus
- Adbrite
- AffiliateSensor
- AllFeeds
- AdEngage
- Adgenta
-----B--------
- BidClix
- Bidvertiser
- BannerBoxes
----C------
- ContextWeb
- CBProSense
- ClicksAdsDirect
- Clicksor
- Chitika
---E----
- Enhance
- ExpoActive (Horrible spammer)
---F---
- Fastclick text ads
----I---
- InfoGrabber
- Interactive
- Intellitxt
---K---
- Kanoodle
---M---
- Miva (FindWhat/Espotting)
---N--
- Nixxie
---Q---
- Quigo
----R---
- RevenuePilot
---S----
- SearchFeed
---T---
- TargetPoint
---V---
- Veoda
---Y---
- YPN
---UK Specific PPC---
- Mirago
- Search123 (ValueClick)
----- A----
- Adhearus
- Adbrite
- AffiliateSensor
- AllFeeds
- AdEngage
- Adgenta
-----B--------
- BidClix
- Bidvertiser
- BannerBoxes
----C------
- ContextWeb
- CBProSense
- ClicksAdsDirect
- Clicksor
- Chitika
---E----
- Enhance
- ExpoActive (Horrible spammer)
---F---
- Fastclick text ads
----I---
- InfoGrabber
- Interactive
- Intellitxt
---K---
- Kanoodle
---M---
- Miva (FindWhat/Espotting)
---N--
- Nixxie
---Q---
- Quigo
----R---
- RevenuePilot
---S----
- SearchFeed
---T---
- TargetPoint
---V---
- Veoda
---Y---
- YPN