i hold an IG index account however they ain't the best, IMHO.
The best by far at the moment is http://www.finspreads.com
Why is it the best you ask?
1. The internet interface is simple to use. and quicker than IG
2. You do not have to set a stop loss and then find that the market goes against you leaving you automatically stop lossed out.
For example with IG you may decide to give yourself a 200 point stop loss and find then you find that the market drops 201 points in this case you are out.
With finspreads you have to put up a margin ( ie dow is X 500 what ever per point you place the bet as ) with that case if it drops 201 points you get a letter saying send more money for the margin cover or sell. The control is with you.
3. This is the best bit you can bet as little as 1p per point. Ig is minimum of £1 This is excellent as it means you can start your account of with £25 and practise your art.
P.S. If you become a good spread better you ain't concerned which way the market moves you trade it up and down.
Also i use http://www.signalwatch.com/
here are some futher thoughts on spread betting.
Tips for spread betters.
1. Be prepared to loose ( you will not always win )
2. Have stop losses ( if the market moves against you admit you were wrong, get out, lick your wounds, be ready to fight again )
3. Look very carefully at the trend of the market your betting. What do you think it will go to, what is the consensus of opinion. As always let the trend be your freind. This is the best site for Dow and Nas http://www.signalwatch.com/
4. Watch for markets with large point moves. IE the dow is 8 point spread and moves very quickly and some days can be 100, 200, 300. so you can make alot ( and lose alot ) of points. The betting on stocks is less likely to give such big movements.
5. Remember spread betting gives you the freedom to bet on falling markets or rising markets.
6. You will need to be able to watch a live chart of the indice you are playing. Personally i bet on the Nasdaq and the dow though normally one at a time.
ftse 100 http://www.londonmoneymarket.com/ie/index.html
dow and nas and S&P http://www.quote.com/quotecom/livecharts/
7. learn pattern recognition Know your charts
try this site. http://www.chartpattern.com/chart_patterns.html
8. Start with small amounts of money per point ( thats why i like finspreads.com ) say 1p a point so if the market goes against you you loose pennys.
9. Remember practise makes perfect
10. Ideally use a chat room as the market is open to see what others think and gain from there experience.