What do you mean by OpenLayers WMS services??
OpenLayers is a JavaScript library to build web maps that can dispaly for example WMS Services.
It is possible to use WMS Services in ArcGIS for Flex API (and I assume it's possible in the javascript API as well).
It might be possible to add a WMS service to a mxd document and publish it in ArcGIS Server (I'm not really sure), but it would be much better to connect directly to the WMS instead of going through ArcGIS Server.
I don't think you can use an ArcGIS Server service in OpenLayers (but actually I have no idea because I don't work with OpenLayers) but you can enable the WMS capability on your ArcGIS Server service and use that WMS service in OpenLayers.
