First of all I am assuming you are using VL 5.8 Standard, not SOHO (you should not be using SOHO with only 184MB of RAM). There are a few things you could do to make it a bit faster, most of what you have to do is use less resource intensive applications and lower your RAM usage, otherwise VL is pretty much maxed out on the speed front.
Firefox is very resource intensive, Opera and SeaMonkey are less so, and Dillo even better (but Dillo's capabilities are limited). You could also substiture IceWM for xfce as your window manager- it would take less RAM and maybe be a bit faster, and can be made to look a lot like Windows XP, but the disadvantages are it is not quite as newbie friendly.
If you stick with xfce remove any unneccessary panel applets that you don't use - some of them consume 16MB of RAM. You might want to consider pre-loading Firefox and aMSN on startup so that users don't experience the load wait time.