Generally you need to go through a webservice that uses the CRM SDK. This is important! You can not write directly to the CRM database. If you do, you invalidate any warranty supplied by Microsoft, and (more importantly) you will probably break CRM to such an extent that you will need to start over (with a fresh install). If you want more info, look at the documentation that comes with CRM and the CRM SDK. Having said that, I have applications that read CRM filtered views, and that does not seem to hurt it. So, getting information out, you can go direct. Getting information in - SDK Only!