I'm currently working on a component of a trading product that will allow a quant or strategy developer to write their own custom strategies.  I obviously can't have them write these strategies in natively compiled languages (or even a language that compiles to a bytecode to run on a vm) since their dev/test cycles have to be on the order of minutes.
I've looked at lua, python, ruby so far and really enjoyed all of them so far, but still found them a little "low level" for my target users.  Would I need to somehow write my own parser + interpreter to support a language with a minimum of support for looping, simple arithmatic, logical expression evaluation, or is there another recommendation any of you may have?  Thanks in advance.
Custom-made modules are going to be needed, no matter what you choose, that define your firm's high level constructs.  
Here are some of the needs I envision -- you may have some of these covered already: a way to get current positions, current and historical quotes, previous performance data, etc... into the application.  Define/backtest/send various kinds of orders (limit/market/stop, what exchange, triggers) or parameters of options, etc...  You probably are going to need multiple sandboxes for testing as well as the real thing.     
Quants want to be able to do matrix operations, stochastic calculus, PDEs.
If you wanted to do it in python, loading NumPy would be a start.  
You could also start with a proprietary system designed to do mathematical financial research such as something built on top of Mathematica or Matlab.
Scripting language for trading strategy development