The first thing you want to consider is what you wish the mixer to do for you:
-how many inputs you need and the split between microphones and line level sources?
-very important...how many outputs do you need? Most mixers just mix, only a few feed direct outputs of each channel for recording.
-does the mixer also need to function as a computer interface, i.e. do you need one with USB or Firewire outputs?
-do you need on-board effects? Probably not for home recording unless you want to add reverb to vocal monitoring.
-what monitoring capabilities do you need? The ability to create several different headphone mixes or just a single one? Again, many mixers are for live use meaning they don't need to feed control room speakers or whatever.
A lot of people involved in home recording assume that having "a mixer" will be a huge help but the reality is that a great many mixers are simply not suitable for recording purposes. Beyond that, unless you have specific things you want to do with the mixer you may find that it doesn't at much at all to your work flow.
Having said that, I'm a fan of having a mixer in my studio--I use mine both as the beginnings of my interface (my mixer feeds ADAT out into an Profire Lightbridge) and, mainly, to create flexible headphone mixes. If you get the right mixer, it can be very useful.
However, before considering makes or budgets, I suggest you have a think about my points above.
Bob
