I agree that dpreview.com can help to provide some guidance as to which would be the best digital camera for you. Aquiring a true manual zoom in your price range is going to be difficult. Though some of the point and shoot cameras, such as the Pentax Optio line do have a manual focus button, it is, of course, nothing more than a way to manually activate the stepper motor used for focusing. It doesn't give a broader variation of focus but does allow you to focus in low-light situations where the camera's focusing algorithms fall short.
I'm sure you're already familiar with the various pros and cons of an SLR verses a point and shoot. I much prefer an SLR for actual picture taking, but I find that a point and shoot is convenient enough that I'm more likely to have it with me and ready to go when the opportunity for a good shot comes along.
Most of the affordable point and shoot digitals allow you to focus far closer than the old 35mm point and shoot cameras do. Many will focus down to under and inch which will provide a pretty close shot. I've had opportunity to work with a Pentax Optio 550, (since replaced with the 555), which can't fit the face of a U.S. dime into a frame at maximum zoom and minimum focal distance. Since that's a 5 megapixel camera, it's sufficient for most macro shots.
As for the shutter lag mentioned, I think that will be a part of digital photography for at least a few more years. I won't go into great detail since I suspect most of those here are already familiar with the workings of a digital camera but it's good to remember all the processing that goes into each image. Each tiny sensor, (pixel) of the CCD can only see one color. That leaves you with only a third of the information required to complete the image. The camera uses an advanced set of calculations to estimate the missing color information for the other two colors for every pixel in the image. Since that's about a hundred calculations per pixel, you begin to understand where some of the lag comes from. Since most of that data processing occurs after the information is captured through the CCD, the majority of the lag is due to the time required for focus lock. I've heard that the Minolta Dimage Z1, Z2 and Z3 cameras utilize a faster AF system which reduces shutter lag substantially.
The only exception I'm aware of to the single color per pixel rule is the Foveon X3 CCD element which can actually detect all three colors at each pixel. Last I'd heard the only commercial camera available with this chip was the Sigma SD9 and the newer SD10 at about £1100.00 for the body alone. Either way, you'll get a greater color range out of 35mm slide film than you will from the 24-bit color of a digital camera. But my experience is that it's very rare to view prints from a 35mm at larger than 4" X 6" so you may find that you're more aware of the detail in a digital shot simply because you're looking at it on a monitor many times the size of a standard print.
As for resolution, I think it's all too easy to get caught up in having more megapixels. If you plan to do a lot of large prints, then it may be worth it to pay for 5 megapixels or more. For most users it's best to remember that most of the shots will be viewed on a computer monitor and standard screen resolutions are still around 1024 X 768 which is about .78 megapixels. In other words, you'll have to reduce the information in the image to less than one megapixel in order to see the whole frame at one time. The advantage to higher resolution outside of more detailed prints of larger sizes, is that it gives you more detail from which to crop the object from an image. For most of my needs, I find 3 or 4 megapixels to be sufficient and even a good 4-megapixel image in JPG format can swallow 2 to 2½ megabytes of your hard drive if set for maximal accuracy and minimal compression.
As for editing software, it's hard not to recommend Adobe Photoshop but the cost of that software alone can more than consume your camera budget. If you're more interested in cropping and minor processing than full-blown editing, many other packages may provide you with adequate capability. One package, called Light Artist allows for some pretty convincing changes to the lighting of the scene after the photo has been taken.
