"I was trying to find a really good book on flash techniques, any ideas? Or should I just go buy a 50mm f1.4 or f1.8 and forget about the flash thing? And again talking about lenses, which one of those I mentioned would you go for, mainly for indoor photography?"Great questions Lisa, and really relevant for someone at your stage of photography.
At some point after you've purchased that entry level sub $1000 dSLR kit with a couple of consumer grade zoom lenses, you're going to want a faster, sharper lens. By faster I mean one with a larger f-stop than the typical f3.5 you're getting at the wide angle setting of the lens in the kits. Remember, a faster lens lets in more light, so you can you can use a faster shutter speed. That's where the term comes from.
Thinking about using flash? Try this blog. http://strobist.blogspot.com Photographer David Honl the blog's author, has some lessons on the right sidebar titled: Lighting 101 archive and Lighting 102 archive. A good place to start. If you are beyond the basics, check out Joe McNally's new book: Hot Shoe Diaries. It's in the left sidebar.
As far as the lens goes, it will come down to price. You could probably pick up a 50mm f1.8 prime lens for ~$125, but for the f1.4 it might cost you ~$400. You could even go crazy and get the f1.2 for $1600 and change. A prime lens is one that has a fixed focal length such as 50mm. A zoom lens on the other hand has a range of focal lengths, for example 24-70mm. Prime lenses tend to cost less and are better quality and faster than zoom lenses. However, they take up space in the camera bag if you need several different focal lengths.
The best way to decide, go to a camera retailer with your own camera and pop each lens on, take a few shots outside and inside with both lenses, plus your own zoom lens set at 50mm. Go home and compare the three. Open each file in Photoshop and view at 100% or more. You want to check edge to edge sharpness at the largest, middle (f8) and smallest f-stop. Use a low ISO to minimize noise and set your camera on Aperture priority.
Even the f1.8 is going to seem like a bright ray of sunshine compared with the consumer grade zoom lenses you've been using so far. My main concern is that without a full frame sensor, it might not be wide enough for you. Remember, unless you are using a full frame sensor, you need to multiply the focal length by approximately 1.5 to get the effective focal length with your entry level camera. So 50mm optically becomes 75mm. If you are shooting indoors, you'd have to have a fairly large room so you get step back far enough to get things in the shot. For portraits, you'll be fine. If you do need a "normal 50mm looking" lens, you may have to consider purchasing a 35mm lens instead. For wide angle, you will have to go to a 20mm or shorter focal length.
You need to consider your long term plan for photography? What types of photography do you see yourself doing? Do you have money set aside to finance your future needs and desires? If you have the budget and want top quality, it will cost more. You will probably want to upgrade your camera body at some point too, but building a lens collection is something that will outlast your camera bodies. I've been using the same lenses for 10 years but have had four different camera bodies in that time, starting with a film camera.
You may also want to look for used lenses. Try places like kijiji or the Buy and Sell. Sometimes people sell packages of film camera gear not realizing they can use the lenses on their digital cameras. Just make sure its the right kind of lens mount. Some older Nikon lenses work on new Nikon bodies, but Canon FD lenses do not work on Canon digital cameras (nor on EOS Canon film cameras). And of course with anything used, take some test photos using your own camera and check them out carefully before plunking down your money.
For reference, in my kit I have:
17-40mm L f4.0 - needed this before I had the full frame sensor
24-70mm L f2.8 - my main and most used lens
70-200mm L f4.0 - for portraits of 1 or 2 people. Keeps you a nice distance away and compresses features nicely. All are Canon L series lenses - good glass!
I'm mainly a fair weather shooter and the f2.8 is fine for what I do, but I'm also keeping my eyes open for a nice 85mm f1.8 prime lens so I can get lovely shallow depth of field when it's wide open.
I also just found a great video on lenses on Scott Kelby's DTownTV. Check out Episode 16 - Lenses Part 1.