Usually, oggdropXPd is the easiest Vorbis encoder (its interface goes like this: set target path and quality, and then just drop files in the window, done). But it only supports lossless files as input (WAV, FLAC, etc).
For general transcoding, it may be interesting to take a look at foobar2000. Even if you dont like foobar as a player (minimalistic UI, too complex options, etc.), you may like it as an encoder and transcoder, for the following reasons:
- it can playback almost any format (popular exceptions are WMA and RealAudio).
- it can encode to ANY format for which a commandline encoder does exist
- it can transcode (convert from one format to another) from all formats which it can playback, to all formats to which it can encode)
- in most cases, it will keep all tags
The result is a tool which can convert almost every audioformat to almost every audioformat.
Configuring foobar for encoding and transcoding goes like this:
1. when installing, make sure to install support for all audioformats which you may want to read. Also make sure that the "converter" gets installed. If neccessary, get support for less popular formats from 3rd party input plugins. (one interesting page is this: http://kode54.foobar2000.org
2. Get commandline encoders for all formats to which you want to be able to encode. Then put all those executables (i.e. lame.exe, oggsenc.exe, etc.) into the foobar folder. First stop for downloading commandline encoders is Rarewares.org: http://www.rarewares.org/ogg-oggenc.php
3. Go into the foobar preferences, then "Tools->Converter". The only important thing here is the "Encoding-Presets"-Area. When you encode or transcode with foobar, you dont manually set the encoding-options everytime. Instead, you pick a preset. You can set the available encoding-presets right here. Some are already added by default. If your preferred setting is not there, just click on "add".
4. Setup done. Now just drag and drop a few source files into the playlist. Mark them with the left mouse button. Rightclick -> Convert -> Convert to..., pick a preset, select output directory, done!
(usual disclaimer: Converting from a lossy format (i.e. mp3) to another lossy format (i.e. ogg vorbis) always results in a slight quality loss. Its as if you first tear a piece from a sheet of paper (mp3), and then tear another piece from it (ogg vorbis). If possible, encode from a lossless source (i.e. CD))