How about a low-budget MIDI controller? Assign and control your sounds that way.
$49.99....
http://www.musiciansfriend.com/srs7/g=key/s=midi/search/detail/base_pid/701522/
(I'm one of the many here who STILL can't master the art of posting a link.)
I confess, I've never used my controller for such purposes but I believe it will work. Spot has forgotten more about MIDI than I'll ever know. Maybe he's cruising the forum today.

I've done a huge amount of sound effect work for live stage productions and my standard method is via CD. Don't use a portable player though because the latency is horrendous. I've got a nice $100 Onkyo player that has essentially instant start. I use pause after playing an effect, then use the cue forward button to move to the next one. Pressing pause to play the effect has a latency of, well ... faster than an eyeblink. It seems like the sound starts playing while i'm still pushing the button in. It's faster and definately more consistant than clicking a mouse button for computer playback.

I'll usually put 10 seconds of silence after each effect so there's plenty of run-off time before the next one starts. The only times i've had problems with that is when there are rapid fire effects. However, almost always i can get a good judge of the timing at a rehearsal and come back the next night with a new CD with that series of effects as a single track and just let 'em rip. Of course, burning the effect tracks in the order they occur in the show is a good idea and saves a lot of headaches. This means that if the telephone rings 18 times in a play, i'll have 18 tracks of telephone rings on the disc. That way there's not much thinking involved; play an effect, pause, cue forward, ready for next effect.

Many players that i've used are often a bit unreliable about starting track 1 properly. That's easy to get around though. Make track 1 10 seconds of silence and start the first effect as track 2.

Another thing i've used in a pinch is a laptop running Sound Forge. Open all the effects in separate windows. Highlight the one you need next and press space bar to play it. This has the advantage in that you don't have to worry about stopping it before the next effect starts. On the other hand, the latency seems a bit random and sometimes there is some skipping or stuttering as it starts playing. I find the CD method to be more stable and reliable.

nonags dawt com has something simple you may be able to use. You'll have to go to their "Free Software for everyone" section. Then a download site, then look in the "Audio Tools" for a program called "Cue Player". It was made for theatre work. I haven't used it or tried it, but I downloaded it once, to see if I could use it for another purpose, which I couldn't . Free, no spyware, no signups.

This is freeware. I have used it in theatrical productions for years.
http://www.world-voices.com/software/nchcart.html


NCHcart is a professional application to cue and play messages, music and advertisements in Radio Stations. It can also be used in larger entertainment venues and supermarkets. Features include:

* Automatic Cue and Sequence Playing
* Automatic Cross Mixing
* Up to 9000 messages can be easily accessed and played
* Immediate access Play
* Runs on Windows 3.1, Windows 95, Windows 98 and Windows NT
* Open audio formats (will play wav files etc directly)