There is apparently no native HDMI-to-VGA on the Mac mini (HDMI is by definition digital-only, but some computer manufacturers route VGA over the HDMI pins when used with an adapter, it appears Apple only supports VGA over the Thunderbolt port this way.)
But, there are companies that make HDMI to VGA adapters that actively convert the HDMI digital signal to a VGA analog signal. Apple sells a third-party one that is marketed toward the AppleTV, but HDMI is HDMI, so it should work with the mini:
http://store.apple.com/us/product/H...ay-mirroring-for-vga-projector-cable?fnode=51
There should be similar ones available elsewhere, possibly cheaper. But they won't be
cheap since they do active conversion.
The other possibility is a Matrox
DualHead2Go adapter that makes two monitors appear to the computer as one single double-wide monitor. (That one plugs directly into the Thunderbolt port and gives you two DP outputs that can each use a DP-to-VGA adapter. They also have one that takes a
VGA input with two VGA outputs. The direct Thunderbolt connection would produce a "less noisy" picture on the monitors, but requires more adapters.)