If you can use adsense, there is nothing even close to it.
Other companies exist only because Google leaves part of the market as peanuts (still it is billions). Those ads and companies usually have much more aggressive formats.
I currently dumped one of the most known: Matomy, because their ads were full of viruses (yes it is common).
UK based I know only Propellerads, but honestly they are weird.
Great is Gunggo, ask for guy named Shaun (shaun (at) gunggo.com, you can tell him you are from Pedro, he is asking me always for ppl who he can trust, so I guess you are the man)
Reasonable for diplay ads is Ybrant.
I can recommend other formats as well, but the question was about banners I think.
If you talk to God, you are praying; If God talks to you, you have schizophrenia.