SketchBook is great, I have a express version
XE currency very useful
Make sure your photos are organised and the best ones synched with the iPad
I find the camera card adapter very useful for uploading photos to iPad when on holiday
Flickr app if you use that service
iCloud to sync your iphone photos automatically
Vimeo and YouTube apps – create logins and feeds so you can easily watch your favourite bike content
BBC iPlayer
Facebook etc if you use those
IAnnotate – outstanding for business use, annotate PDFs and Word docs
You should think about some DVD ripping / conversion software so you can upload any movie to the iPad
The software which comes as standard is very useful, bookmark icons on home page for favourite sites. I switch between the standard mail application and specific gmail app (each have their merits)
Consider a way to connect the iPad to tv, you can do this via £25 cable or £100 apple tv – very useful for watching content downloaded from web (eg BC iPlayer) listening to music etc