@Thomas108:
With the Articles-Extra you have the possibility to create a rss-feed from your blog. (
http://rtfm.modx.com/display/ADDON/Articles.Creating+a+Blog)
After you have done that, open the rss-feed-link and take a look if everything works fine.
If the rss works correctly, you have to register a
dlvr.it-account.
There you can add the link of your rss-feed as Source (left side) and on the right side, you can add the destinations (for example facebook, twitter and many more).
And thats it. If your rss-feed is connected to facebook for example, dlvr.it checks your rss-feed from time to time and if there is a new blogpost it automaticly posts the news as a status on facebook. That is really nice and saves you a lot of extra-time and work.
You also can do other route-variations like Facebook -> Twitter (what I have done a few weeks ago for a client). Everytime you post a status on Facebook, dlvr.it automaticly posts a tweet from that in Twitter. It's really nice.
But remember to do not loops... For example,
FB -> Twitter and Twitter -> FB because then, you get crossposts all the time ;-)
Another great service with a little bit more complexity as dlvr.it is
https://ifttt.com/ (IFTTT = "If This Than That") what does almost the same as dlvr.it, but you can add more route-options.
On that page here
https://ifttt.com/wtf you can find some examples for "recipes" (or routes) you can define.
For example, if you take a photo with instagramm, you can automaticly upload it to dropbox via ifttt.
So long, I hope it helps ;-)
Greetings
Jens