Program to convert flac to mp3?

foobar2000 (on Windows) has a built-in, multi-format converter. To convert to mp3, you need to download the LAME mp3 encoder binary files; foobar2000 will ask for the location of lame.exe before converting.

xrecode II preserves album art and other metadata, and is fast -- it uses all available cores. It's shareware, and works very well on Windows 7.

ffmpeg -i input.flac -ab 196k -ac 2 -ar 48000 output.mp3

I'm not sure if it keeps tag and metadata. If FFmpeg doesn't work, for what platform do you need your converted (Windows, OSx, Linux) ?