Sometimes resources for younger students can be useful for lower secondary age students, see for example Mark Robinson’s Numberlines from the old Ambleside Primary School site which includes an option to display a number line from -5 to 5.
For another excellent number line resource see J Barrett’s Numberline Jump Maker on ictgames.com. I often recommend that students sketch a number line to help with addition and subtraction problems and very clear resources like these can really help. Teacher Resources on Line includes a Big Number Line under Basic Materials for display on a classroom wall
Further resources include exercises from Trinity School in Nottingham (under Number) and Interactive Resources from CIMT (see unit 3, 3.3 on Negative Numbers and Unit 15, 15.1 and 15.2 for operations with negative numbers in the tutorials section).
There are many excellent resources on TES, the resource collections includes a section on Topic Specials which includes 10 of my favourite resources on Negative Numbers.