Bet365 is a huge UK company (one of the biggest private companies in the UK) and is one of the most famous bookmakers around. Therefore you can generally be assured of several things.
A) Fast payouts
B) Descent support

I'll be honest and say I had never heard of Sun Poker until I was looking through various poker forums and saw them advertised as such I was a bit dubious but thought I would give them a quick try anyway.
Upon visiting their website they offer a massive deposit bonus of $1,000 from a $500 deposit which seems to good to be true not to mention this a monthly bonus!! upon checking out the terms and conditions a bit further you will need to gather 9,000 points in order to release the full amount.
In order to achieve these points you need to wager the following:
Rake from 0 to 24 = 0 MPP

As a poker addict myself I have come accross many MANY stupid comments on poker tables, from idiots trying to make arguments over a $0.05 loss to donks trying to coach the much more experienced players. Here are some of my Fav::

High Stakes Poker Series 4 episode 14
Jamie Gold and Sammy Fahra were involved in a big pot, Sammy was ahead with AA against Golds KK. Every knew exactly what Gold had including Sammy but he refused to raise the river. Later on Doyle Brunson Comments:
“I don’t know, are you sleeping with him or what?”

The one thing that first struck me with Titan Poker is the amount of promotions they run!
Current promotions include a $2,000,000 guranteed tournament on March 2nd 2008.
Holiday promotions (such as Valentines day promotions, christmas and new year etc) These basiclly involve playing any standard ring games and being entered in to a prize draw. Prizes vary on the compeition etc.
$100,000 Omaholics promotion. This doesn't just involve a great pun, basiclly the player who plays the most raked hands over 2 months can walk away with up to $100,000

Backed by poker legend Johnny Chan this site offers some very good promotions such as a $1,000 deposit match! (one of the biggest in the industry) tournaments have been run in the past where you can actually win lesson with the man himself!
Johnny chan is the winner of 10 WSOP bracelets and millions in tournament winnings. Quite how much involvement Chan has in running the site is currently unknown though.

The first thing I heard about PKR.com was that the unique software creates immense 3D environments giving a supposdely more 'realistic' game play. Thanks to this feature I believe there will be a lot more fish playing here as the sort of people that play here are more in to their 3d communities and pretty graphics then truely understanding how poker works. So if it's fish your looking for then this may well be the place for you.

It was at Full Tilt Poker I first started playing STT for buying of around $10-$20. You can play tournaments in order to release the bonus. Initially I deposited just $50, got my $50 free and made my first withdrawl of $200 after winning several STT. My initial deposit was made from my card and my withdrawl was credited back to my card within 7 days.
There are not as many fish playing on FTP as there are on sites such as PokerStars.com and PartyPoker.com however I have had some success playing on the lower limit tables $0.10/$0.20 area.

Virgin Casino is part of the massive virgin group so not only can you be reassured that they aren't just a fly by night casino, you are also playing with one of the biggest companies in the UK so customer support, fast and reliable payouts are the norm!