Help. Is This Normal?

seems normal. Safari's memory usage is a bit on the high side though. my memory usage is 435 MB active with Safari, iCal and iTunes open. you can always quit Safari if your system starts to slow down.

have a look here for a detailed briefing on memory in Mac OS X from Apple.

Its ok. Read how OS X handles RAM.

True about Safari. When I checked the Processes readings in my iStat, Safari uses more RAM than my Opera. I have only one tab open in Safari while the Opera has 9 tabs and the transfer window is downloading a file.

Unix systems tend to over allocate memory and leave it allocated. The principle is that memory is faster, so it almost always over allocates and leaves it there for the programs to dip in an out of. Its common to see all of your ram allocated with only a few programs running, but its a not bad thing - you WANT to use your ram. Ram is always faster then swap. If you see your system using a lot of swap then you really did run out of memory and may need re-evaluate your memory situation.

In contrast, Windows spends all of its time trying to keep memory free (un allocated for application use). And whats the point? Because the next time you run that program it will need to spend all that time reallocating the memory again.