The following are some sites that I've found very useful and who offer a quality service. None of these are paying to be on this page, these are just my personal recommendations.
Fun and effective vocal tuition. Based in Hemel Hempstead, Herts. Covers a range of styles including Pop, R&B, Soul.
Sheet Music and Audition Preparation
An excellent online service providing backing tracks with vocal guides for auditions or rehearsing
One-stop shop for business cards and stationery. Loads of templates, real easy to use. I've used them a number of times and the service is always first-class.
In my opinion, THE site for MIDI or Audio backing tracks. You can audition every track before buying, and each track costs around 60p. Instant download and no minimum purchase restrictions. Wide range of styles.