Looks like you can. I found this answer at the link listed below:
I have exactly the setup you describe, with a 2010 Mac Mini, with three Samsung 245BWs even. The same setup will work with a 2011 Mini as well. Just don't get anything older.
In my rig, one monitor is connected to the Mini's mini-DisplayPort port (with a mini-Displayport to HDMI cable), one is connected to the Mini's HDMI port (with an HDMI-DVI adapter), and the third is connected using a DisplayLink USB dongle of dubious Chinese manufacture.
All three run at the monitor's default 1920x1200 resolution. The two 'real' connections are fast and great for video and games, but the USB one is noticeably slower for video, so I deliberately use that one for e-mail, web, iTunes, and all those other 'on the side' applications.
The same would work with a 2011 (current) Mini, just sub in "Thunderbolt port" for mini-DisplayPort above.
When choosing a USB/HDMI adaptor, the key word you want is DisplayLink, and you must watch the specs VERY closely to be sure that 1920x1200 is supported. Many only work up to 1080, which is not quite enough. It took me three tries.