This is from a site which is quite interesting, and its material seems to not be the usual copy-and-paste stuff you can find on other sites. Sadly, the invention capability of most Dawah sites is minimal, usually it's just a collection of articles copied from another site packaged in a new look.
So insha'Allaah this site which I found seems to provide some fresh own-written articles (with a few exceptions). Not all material on this site are perhaps completly sound, but I found no fault in the Dawah articles which I'm going to link to, insha'Allaah:
Enlightened Thinking
Proof of God
Need for Messengers
Proof of Qur'an
And here is the original site: http://www.caliphate.co.uk