What are the causes of proteinuria?

Proteinuria may be a feature of the following conditions:
Nephrotic syndromes (i.e. intrinsic renal failure)
Pre-eclampsia
Eclampsia
Toxic lesions of kidneys
Collagen vascular diseases (e.g. systemic lupus erythematosus)
Dehydration
Glomerular diseases, such as membranous glomerulonephritis, focal segmental glomerulonephritis, minimal change disease (lipoid nephrosis)
Strenuous exercise
Stress
Benign orthostatic (postural) proteinuria
Focal segmental glomerulosclerosis (FSGS)
IgA nephropathy (i.e. Berger's disease)
IgM nephropathy
Membranoproliferative glomerulonephritis
Membranous nephropathy
Minimal change disease
Sarcoidosis
Alport's syndrome
Diabetes mellitus (diabetic nephropathy)
Drugs (e.g. NSAIDs, nicotine, penicillamine, gold and other heavy metals, ACE inhibitors, antibiotics, or opiates (especially heroin)
Fabry's disease
Infections (e.g. HIV, syphilis, hepatitis, poststreptococcal infection, urinary schistosomiasis)
Aminoaciduria
Fanconi syndrome
Hypertensive nephrosclerosis
Interstitial nephritis
Sickle cell disease
Hemoglobinuria
Multiple myeloma
Myoglobinuria
Organ rejection: Kidney transplant patients may have gamma-globulins in their urine if the kidneys start to reject.
Ebola hemorrhagic fever
Nail patella syndrome
Familial Mediterranean fever
HELLP Syndrome
Systemic lupus erythematosus
Wegener's granulomatosis
Rheumatoid arthritis
Glycogen storage disease type 1
Goodpasture's syndrome
Henoch Schonlein Purpura
A urinary tract infection which has spread to the kidney(s)

I know that's not overly helpful, but there are some fairly benign causes (drug causes) to severe ones like Lupus.