Carbon fibre is lighter than aluminium, but can cost significantly more money.
If using a DSLR, you definately want some
weight to it, otherwise it will fall over and won't be as stable for the images.
Manfrotto have the 055 and the 190 series, I believe. Within those two categories, you have different models, for instance some will tilt and some won't. I would have a look on their website. I am still looking to get one. I currently use a Monopod though, which was bought for easiest in all respects, and to save money.
Aluminium or Carbon Fibre
The number of legs (the more legs, the more compact, and therefore more expensive)
The features - does it tilt?
The maximum weight - this varies, and the head should also be considered
The domestic style tripods, the type of thing that you see available for £15 at your local camera shop have fixed heads, are extremely lightweight, and not really suitable for DSLRs. You ideally want a professional style one.
The Professional style tripods are available with or without heads. If you are happy to purchase a particular tripod and head that is available in a kit, you can take for a discounted price. I have noticed though that Monopods don't really come in kits though.
When buying, I would look at both ebay and Google 'Shopping' (tab). Within Cameralabs, there are affiliated sponsored links which means when the purchase is made, Cameralabs will receive something, which goes towards running the site.