This post is the further discuss for this article:
http://www.mobabel.net/mobabel/blog/millennial-media-mobile-advertising-...

I am always looking for one solution that can integrate Ads into J2ME,  and indeed i found some Ads companies support J2ME SDK or they offer open API that you can use to develop yours own ads SDK.

1, as described in that article, Millennial Media offer open ads API then you can dev your own ad SDK.

2. smaato , it offers BlackBerry SDK, i really wonder why they dont offer no more J2ME SDK from 2 years ago. I have checked the Blackberry SDK source code, in practice, this SDK can be wrapped to J2ME SDK, most of the source code can be used, you need rewrite the XML parser and graphic UI because it use Blackberry native sdk. But i will not take this risk, it must be some reason that why Smaato does not support J2ME, such investigation could ban your account(i am afraid)

3. Adfonic, it offer J2ME SDK, with online document you can implement ads not so difficult; BUT, i can not get ads during the test. They have good support, and i wrote them about this problem, they answer me quickly and sent me one new version of SDK. I have tried, but stll could not get ads. Lastly, i know the reason, the developer form Adfonic told, the app need to be signed then can get the right ads.
This is embarrassed situation, i need to pay more than 500 dollor/year to buy the certificate for showing ads and i am not sure whether i can earn 500+ dolloer per year. I give it up.

4. vserv, it offers J2ME SDK, full screen ads, sounds good, company locates in India, i tired to register but when i login i always got login problem.

5. inneractive , it offers J2ME SDK, support Paypal payment. I have tested, it is fit for Game, not for application app, because it shows a full screen ad when starting app, i have not found api to set the ad size.

If you know any other companies, or you have experience to dev your own Ads sdk, welcome to leave comment here!!

refer:
http://www.nokiaviews.com/2010/09/how-to-make-money-in-ovi-store-with-ads.html