There are plenty of tools on the market that will allow for this. One that I have used in the past is INFO-Pump. It a fairly robust tool that allows for data migration across all platforms. I have used it to link Sybase, DB2, Lotus notes all intoone integrated system. I know for a fact that it supports both Oracle and SqlServer. This product will allow you to mix and match data from multiple databases into one or many. It's a good solid tool. Here's a link if you want to look it up.
http://www.platinum.com/products/dataw/inpumps.htm#pi
I'm sure there are probably other tools out there as well, another that I know of is Replic-Action although this is more for Lotus Notes integration to other systems it does connect to SqlServer and Oracle and may also be of assistance to you.
good luck with whatever you choose.
-Mike