I'm mrkipling, creator of Maraschino. It's a web-based frontend for your XBMC-based HTPC that allows you to view and control the common stack of open-source technologies that you are likely to have on your HTPC.
It has an SABnzbd module which allows you to view what is currently downloading, see what else is in your queue, pause/resume items, and allows you to pause/resume and change the speed of what is currently downloading.
You can also search Usenet (currently newnzab and NZBmatrix) from within Maraschino and send results directly to SABnzbd at the click of a button.
There are also modules for Sickbeard (that allow you to view SB information such as upcoming episodes, but also add and search for new shows). There are also uTorrent and Transmission modules. Plus a whole bunch of other modules, basically.
It also fully integrates with XBMC - you can see what movies and TV show shows have been recently added, browse your media library, play items with the click of a button, and much more.
There is also a "remote control" mode - you can use your physical keyboard (via the web browser that you are using to access Maraschino) to control whichever XBMC installation you have selected (as you can define multiple ones).
Basically, it's a web-based dashboard for your XBMC-based HTPC, and SABnzbd is just a small part of what you can view and control using it.
You can find the project homepage here: http://www.maraschinoproject.com/
There is a thread on the XBMC forums here: http://forum.xbmc.org/showthread.php?tid=113136
Plus we have also recently added forums.
Here's a screenshot!
In particular the SABnzbd module:
Hope you find it useful.
And sorry for the shameless self-promotion (reading back, trying to get all the best features in, in reads kinda like a hard-sell!) - but it does tie in quite well with SABnzbd, so thought it probably worth mentioning in these forums.